Electrodes, batteries, and battery packs

Abstract

Provided, according to an embodiment of the present invention, is an electrode having an active material-containing layer including: an active material comprising a titanium-containing oxide; and an aluminum oxide compound present on the surface of the active material. Forms of the titanium-containing oxide include primary particles and aggregates containing a plurality of primary particles. According to a radial distribution function obtained by Fourier transform of an extended X-ray absorption fine structure spectrum of the K-edge of aluminum of the active material-containing layer, the value of the peak intensity ratio IA / IB, where peak A appears between 1.1 Å and 1.5 Å and peak B appears between 2.8 Å and 3.2 Å, is 3.5 to 9. The smallest square circle diameter Dg of the aggregate is at least 1 / 20 but less than 1 / 2 with respect to the thickness Te of the active material-containing layer.

Description

[Technical Field]

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

[0002] Lithium-ion secondary batteries, which charge and discharge by the movement of lithium ions between the positive and negative electrodes, are widely applied in applications ranging from small devices such as portable electronic equipment to large-scale applications such as electric vehicles and power supply and demand adjustment, taking advantage of their high energy density and high output.

[0003] Instead of carbon materials, the negative electrode active material has a lithium absorption / desorption potential of approximately 1.55V (vs.Li / Li) relative to the lithium electrode. + Non-aqueous electrolyte batteries using spinel-type lithium titanate, which has high performance, have also been put into practical use. Spinel-type lithium titanate has excellent cycle performance because it undergoes little volume change during charging and discharging. In addition, because lithium metal is not deposited during lithium absorption and release in negative electrodes containing spinel-type lithium titanate, secondary batteries equipped with this negative electrode can be charged at high currents and low temperatures. To further improve high-current and low-temperature performance, attempts are being made to coat the spinel-type lithium titanate particles with aluminum oxide compounds. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-169276 [Non-patent literature]

[0005] [Non-Patent Document 1] B. Ravel and M. Newville, ATHENA, ARTHEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT, Journal of Synchrotron Radiation 12, 537-541 (2005) [Overview of the project] [Problems that the invention aims to solve]

[0006] The objective is to provide an electrode that suppresses electrical resistance and resistance rise, enabling the realization of a battery with excellent energy density and low-temperature performance, a battery equipped with this electrode, and a battery pack equipped with this battery. [Means for solving the problem]

[0007] According to the embodiment, an electrode is provided comprising an active material-containing layer comprising an active material containing a titanium-containing oxide and an aluminum oxide compound on the surface of the titanium-containing oxide. The form of the titanium-containing oxide includes primary particles and aggregates containing a plurality of primary particles. The active material-containing layer includes a peak A appearing in the range of 1.1 Å to 1.5 Å and a peak B appearing in the range of 2.8 Å to 3.2 Å in the radial distribution function obtained by the Fourier transform of the broad-field X-ray absorption fine structure spectrum of Al's K absorption edge. B Peak intensity I of peak A A Ratio I A / I B The value is between 3.5 and 9. The least squares circle diameter D of the aggregate. g The thickness T of the active material-containing layer e It is between 1 / 20 and less than 1 / 2.

[0008] In another embodiment, a battery is provided that comprises a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes the electrode described above.

[0009] In yet another embodiment, a battery pack is provided, which includes the battery described above. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic plan view showing an example electrode according to the embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view of the electrode shown in Figure 1 along the line II-II. [Figure 3] Figure 3 is a conceptual diagram showing a partial example of a binarized cross-sectional image of an electrode according to the embodiment, obtained using a scanning electron microscope. [Figure 4] Figure 4 is a conceptual diagram showing some other examples of a binarized cross-sectional image of an electrode according to the embodiment, obtained using a scanning electron microscope. [Figure 5] Figure 5 is a conceptual diagram showing another example of a binarized cross-sectional image of an electrode according to the embodiment, obtained using a scanning electron microscope. [Figure 6] Figure 6 is a graph showing the radial distribution function obtained by the Fourier transform of the broadband X-ray absorption fine structure spectrum of Al at the K absorption edge for the surface of an example electrode according to the embodiment. [Figure 7] Figure 7 shows a cross-section of an example battery according to the embodiment, cut in the thickness direction. [Figure 8] Figure 8 is an enlarged cross-sectional view of section E in Figure 7. [Figure 9] Figure 9 is a partially cutaway perspective view of a battery in another example according to the embodiment. [Figure 10] Figure 10 is an exploded perspective view of an example battery pack according to the embodiment. [Figure 11] Figure 11 is a block diagram showing the electrical circuit of the battery pack shown in Figure 10. Embodiment

[0011] It has been reported that coating active material particles with an aluminum oxide compound has the effect of improving the increase in resistance. However, since the aluminum oxide compound is insulating, the initial resistance increases by including the aluminum oxide compound. Therefore, the coating with the aluminum oxide compound has a problem that the charge-discharge rate performance deteriorates.

[0012] Embodiments will be described below with reference to the drawings. In the embodiments, the same reference numerals are assigned to common configurations, and redundant descriptions are omitted.

[0013] Also, each figure is a schematic diagram for facilitating the explanation and understanding of the embodiments. Although there are parts where the shape, dimensions, ratio, etc. are different from the actual device, these can be appropriately redesigned in consideration of the following explanation and known techniques.

[0014] (First Embodiment) According to the first embodiment, an electrode is provided. The electrode includes an active material-containing layer containing an active material and an aluminum oxide compound. The active material includes a titanium-containing oxide. The aluminum oxide compound is on the surface of the titanium-containing oxide. The form of the titanium-containing oxide includes primary particles and aggregates containing a plurality of these primary particles. In the radial distribution function obtained by Fourier transform of the extended X-ray absorption fine structure spectrum at the K absorption edge of Al for the active material-containing layer, it includes peak A appearing in the range of 1.1 Å or more and 1.5 Å or less and peak B appearing in the range of 2.8 Å or more and 3.2 Å or less. The peak intensity I B of peak A with respect to A the peak intensity I A of peak B, the ratio I B / I g is 3.5 or more and 9 or less. The least-squares circle diameter D e of the aggregate is 1 / 20 or more and less than 1 / 2 with respect to the thickness T

[0015] The electrode according to the embodiment may be an electrode for a battery. Examples of batteries that may contain the electrode according to the embodiment include secondary batteries such as lithium-ion secondary batteries. Secondary batteries include non-aqueous electrolyte secondary batteries containing a non-aqueous electrolyte. The electrode may be, for example, a negative electrode for a battery.

[0016] Secondary batteries equipped with a negative electrode containing titanium oxide offer superior cycle life and storage performance, as well as the ability to charge and discharge at high currents and charge under low-temperature conditions. To further improve these high-current and low-temperature performance, attempts are being made to reduce the size of the active material particles. While reducing the size of the active material particles improves input / output performance, it also presents the challenge of increased resistance due to surface side reactions.

[0017] The present inventors have diligently conducted research to solve this problem concerning non-aqueous electrolyte batteries equipped with a negative electrode containing a titanium-containing oxide, and as a result have discovered an electrode according to the first embodiment. Specifically, they have found that by presenting a specific aluminum oxide compound on the surface of the titanium-containing oxide, the increase in resistance due to surface side reactions can be suppressed, and by agglomerating some of the particles, the increase in resistance can be suppressed while improving rate performance and energy density.

[0018] The electrode according to the first embodiment is an electrode containing a titanium-containing oxide as an electrode active material, wherein an aluminum oxide compound is present on the surface of the titanium-containing oxide particles. In the active material-containing layer of the electrode, the titanium-containing oxide coated with the aluminum oxide compound exists in two states: as primary particles and as aggregates formed by the aggregation of primary particles. The radial distribution function obtained by the Fourier transform of the wide-field X-ray absorption fine structure (EXAFS) spectrum of Al at the K absorption edge for the electrode surface includes a peak A appearing in the range of 1.1 Å to 1.5 Å and a peak B appearing in the range of 2.8 Å to 3.2 Å. Peak intensity I of peak B B Peak intensity I of peak A A Ratio I A / I B The value is between 3.5 and 9. The aggregate has a least squares circle diameter Dg The thickness T of the active material-containing layer e The electrode has a size that is between 1 / 20 and less than 1 / 2 of the original electrode. With this configuration, the electrode can provide a battery that has good rate performance, suppresses resistance increase during storage, and has excellent low-temperature output performance.

[0019] The mechanism by which such electrodes improve storage performance is not fully understood, but it can be thought of as follows:

[0020] Reducing the primary particle size of the active material particles, for example to 1 μm or less, increases the specific surface area, thereby improving the lithium ion acceptance performance of the active material itself. However, as the primary particle size decreases, the proportion of active sites on the surface of the active material increases. As a result, side reactions between the active material and electrolytes increase, leading to an increase in electrical resistance during storage.

[0021] The presence of aluminum oxide compounds in a specific state on the active material surface can suppress side reactions with the electrolyte, etc. Specifically, the radial distribution function obtained by the Fourier transform (FT-EXAFS) of the EXAFS spectrum of Al contains peak A in the range of 1.1 Å to 1.5 Å and peak B in the range of 2.8 Å to 3.2 Å, and the peak intensity ratio of these peaks is I A / I B In electrodes where the value is between 3.5 and 9, it is determined that the aluminum oxide compound is present on the active material surface in a state that is effective in suppressing the above-mentioned side reactions. It is thought that at least a portion of the aluminum oxide compound condenses with functional groups that can act as active sites on the active material surface, thereby suppressing the side reactions.

[0022] Furthermore, some of the titanium-containing oxide contained within the electrode exists as aggregates formed by the aggregation of primary particles. For example, aggregates of titanium-containing oxide can be formed by the reaction of alcohol contained in a solution of an aluminum alkoxide compound, which can function as an aluminum oxide compound source, with a binder that may be included in the electrode along with the active material. When lithium ions are inserted, for example, when an electrode containing titanium-containing oxide as the negative electrode active material is charged, the titanium-containing oxide exhibits conductivity. Therefore, in electrodes with the above configuration, when a large current is applied for a short period of time, the current concentrates in the aggregates where the gaps between grain boundaries are small. This reduces the electrical resistance (IR drop) during short-term use. Moreover, as mentioned above, the coating with an aluminum oxide compound suppresses side reactions on the surface of the active material, which is thought to suppress uneven degradation during high-current use. Furthermore, it is possible to provide a battery with excellent low-temperature performance.

[0023] The coexistence of primary particles and aggregates of titanium-containing oxide within the active material layer enables dense packing of the active material. As a result, the electrode exhibits superior energy density.

[0024] The least squares circle diameter D of the aggregate g However, the thickness T of the active material-containing layer e The probability is 1 / 20 or greater and less than 1 / 2 (1 / 20 ≤ D g / T e < 1 / 2). Least squares circle diameter D of the aggregate. g For example, it can be within the range of 4 μm to 20 μm.

[0025] Next, the electrode according to the first embodiment will be described in more detail.

[0026] The electrode includes an active material-containing layer (electrode composite layer) and may further include a current collector. The active material-containing layer may be formed, for example, on one side or both sides of a strip-shaped current collector. The active material-containing layer may include an active material, an aluminum oxide compound, and optionally a conductive agent and a binder.

[0027] The active material includes, for example, a titanium-containing oxide having an average primary particle size of 600 nm to 1 μm. Preferably, the titanium-containing oxide includes a lithium-titanium composite oxide. An electrode containing a titanium-containing oxide, such as a lithium-titanium composite oxide, exhibits a redox potential of 0.4 V (vs. Li / Li) relative to the oxidation-reduction potential of lithium. + Since it can exhibit a Li storage potential of ) or higher, it is possible to prevent the deposition of metallic lithium on the electrode surface when high current input and output are repeated. The titanium-containing oxide is particularly preferably a lithium titanium composite oxide having a spinel-type crystal structure. As a specific example of such a spinel-type lithium titanium composite oxide, Li 4+a Ti5O 12 Lithium titanate having a spinel structure can be given as an example, where the value of the subscript a changes with charge and discharge within the range of 0 ≤ a ≤ 3.

[0028] The titanium-containing oxide is coated with an aluminum oxide compound. The titanium-containing oxide coated with the aluminum oxide compound exists in the active material-containing layer in two states: as primary particles and as aggregates formed by the aggregation of primary particles. Here, an aggregate refers to a group of active material in which, when the image obtained by observing a cross-section of the active material-containing layer with a scanning electron microscope (SEM) is binarized for the active material (titanium-containing oxide) and voids, there are no "0"s inside, and when the image obtained by observing with a transmission electron microscope (TEM) is observed, the element of aluminum can be confirmed inside by energy-dispersive X-ray spectroscopy (EDX). For example, the "aggregates" in each embodiment are distinct from secondary particles that have internal voids. In addition, the "aggregates" in each embodiment are also distinct from secondary particles that were composed of secondary particles before being coated with the aluminum oxide compound. The active material particles in the center of the aggregates are coated with the aluminum oxide compound, but the active material particles in the center of secondary particles, such as those given as examples here, are not coated with the aluminum oxide compound. The presence of aluminum oxide compounds not only on the outer periphery of the aggregates but also on the surface of primary particles located inside the aggregates suppresses side reactions between the electrolyte and the active material that gradually permeate over time. It is desirable that the secondary particles of the titanium-containing oxide contained in the active material layer of such electrodes are all aggregates as described above. SEM observation will be described in detail later. In addition to titanium-containing oxides, the aggregates may further contain aluminum oxide compounds and binders.

[0029] The active material may contain additional active materials other than the titanium-containing oxide mentioned above. For convenience, the active material containing the titanium-containing oxide mentioned above will be referred to as the "first active material," and any other additional active materials will be referred to as the "second active material." If the second active material is further included in addition to the first active material, the second active material may be 0.4V(vs.Li / Li +It is desirable to use an active material that can exhibit a Li storage potential of ) or higher. If a second active material is included, the mass ratio of the second active material to the first active material is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less.

[0030] Aluminum oxide compounds can coat the surface of active materials containing at least titanium oxides, thereby suppressing the increase in resistance. For example, aluminum oxide compounds are derived from aluminum oxide compounds.

[0031] Conductive agents can enhance current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as acetylene black, carbon black, graphite, carbon nanofibers, and carbon nanotubes. These carbonaceous materials may be used individually or in combination.

[0032] A binder can have the effect of binding the active material, conductive agent, and current collector together. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, acrylic resin and its copolymers, polyacrylic acid, and polyacrylonitrile.

[0033] The mixing ratios of the active material, conductive agent, and binder are preferably within the following ranges: 70% to 97.5% by mass for the active material, 2% to 20% by mass for the conductive agent, and 0.5% to 10% by mass for the binder. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer is improved, and excellent high-current performance and low-temperature performance can be expected. Furthermore, by setting the amount of binder to 0.5% by mass or more, sufficient bonding between the active material-containing layer and the current collector is achieved, and excellent lifespan performance can be expected.

[0034] On the other hand, from the viewpoint of increasing capacity, it is preferable that the conductive agent and the binder each be 20% by mass or less, and more preferably 10% by mass or less.

[0035] Area S of the cross-section of the active material-containing layer E In contrast, the cross-sectional area S of the aggregate occupying that cross-section. G Ratio S G / S E It is preferable that the ratio is between 1 / 200 and 1 / 4. When the proportion of aggregates in the active material is such that the total cross-sectional area of ​​aggregates accounts for between 1 / 200 and 1 / 4 of the cross-section of the active material-containing layer, primary particles of the active material can enter the gaps between the aggregates. Therefore, electrodes like the one described above have excellent energy density.

[0036] The current collector is preferably formed from aluminum foil or aluminum alloy foil containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 20 μm or less, and more preferably 15 μm or less.

[0037] Next, a specific example of the electrode according to the first embodiment will be described with reference to the drawings.

[0038] Figure 1 is a partially cutaway plan view schematically showing an example of such an electrode. Figure 2 is a cross-sectional view along the line II-II in Figure 1. Here, an example of a negative electrode is shown.

[0039] The negative electrode 4 shown in Figures 1 and 2 comprises a negative electrode current collector 4a and a negative electrode active material containing layer 4b provided on the surface of the negative electrode current collector 4a. The negative electrode active material containing layer 4b is supported on the main surface of the negative electrode current collector 4a. The negative electrode active material containing layer 4b may be provided on both the front and back main surfaces of the negative electrode current collector 4a, as shown in Figure 2. Alternatively, the negative electrode active material containing layer 4b may be provided on only one main surface of the negative electrode current collector 4a.

[0040] Furthermore, the negative electrode current collector 4a includes a portion on its surface where the negative electrode active material-containing layer 4b is not provided. This portion functions, for example, as a negative electrode current collector tab 4c. In the illustrated example, the negative electrode current collector tab 4c is a narrow portion that is narrower than the negative electrode active material-containing layer 4b. The width of the negative electrode current collector tab 4c may be narrower than the width of the negative electrode active material-containing layer 4b, or it may be the same width as the negative electrode active material-containing layer 4b. Instead of the negative electrode current collector tab 4c, which is part of the negative electrode current collector 4a, a separate conductive member may be electrically connected to the negative electrode 4 and used as an electrode current collector tab (negative electrode current collector tab).

[0041] The negative electrode active material-containing layer 4b contains a negative electrode active material containing titanium oxide. The negative electrode active material is contained in the negative electrode active material-containing layer 4b in the form of primary particles and in the form of aggregates 4d formed by the aggregation of primary particles. In Figure 2, the depiction of each primary particle forming the aggregates 4d is omitted. In addition to the negative electrode active material, the negative electrode active material-containing layer 4b may further contain a conductive agent and a binder. In Figure 2, the components other than the aggregates 4d contained in the negative electrode active material-containing layer 4b (other active materials such as titanium oxide in the form of primary particles, conductive agent, binder) are omitted, and the portion of the negative electrode active material-containing layer 4b other than the aggregates 4d is schematically represented.

[0042] Thickness T of the negative electrode active material containing layer 4b e In contrast, the average least squares circle diameter D of the aggregates 4d contained in the negative electrode active material layer 4b g (Figure omitted) is 1 / 20 or more and less than 1 / 2.

[0043] In aggregate 4d, the active material particles constituting aggregate 4d are in close proximity, and their grain boundaries are not separated. Therefore, current 10 flows more easily through the aggregate 4d portion than through the rest of the negative electrode active material-containing layer 4b. Consequently, during short-term high-current current application, the current 10 concentrates in aggregate 4d.

[0044] Electrode Manufacturing The electrode in question can be manufactured as follows.

[0045] First, an active material containing titanium oxide is prepared. Titanium oxide can be synthesized, for example, by a solid-phase method. Titanium oxide can also be synthesized by other wet synthesis methods such as the sol-gel method and the hydrothermal method.

[0046] First, prepare a Ti source and a Li source according to the desired composition. These raw materials may be compounds such as oxides or salts. For the Li source, lithium hydroxide, lithium oxide, lithium carbonate, etc., can be used.

[0047] Next, the prepared raw materials are mixed in an appropriate stoichiometric ratio to obtain a mixture. For example, Li4Ti5O 12 When synthesizing the spinel-type lithium titanium composite oxide represented by [formula], titanium dioxide (TiO2) and lithium carbonate (Li2CO3) can be mixed such that the molar ratio of Li to Ti in the mixture is 4:5.

[0048] When mixing the raw materials, more than the specified amount of Li may be added. In particular, since there is concern that Li may be lost during heat treatment, more than the specified amount may be added.

[0049] In the wet process, the raw materials are dissolved in pure water, and the resulting solution is dried while stirring to obtain a calcination precursor. Drying methods include spray drying, granulation drying, freeze-drying, or a combination thereof.

[0050] Next, the mixture obtained from the previous mixing or the calcination precursor is heat-treated at a temperature of 750°C to 1000°C for a period of 30 minutes to 24 hours. Below 750°C, sufficient crystallization is difficult to obtain. On the other hand, above 1000°C, grain growth progresses too much, resulting in coarse particles, which is undesirable. Similarly, if the heat treatment time is less than 30 minutes, sufficient crystallization is difficult to obtain. Also, if the heat treatment time is longer than 24 hours, grain growth progresses too much, resulting in coarse particles, which is undesirable. Calcination may be carried out in air. Alternatively, calcination may be carried out in an oxygen atmosphere, nitrogen atmosphere, or argon atmosphere.

[0051] It is preferable to heat-treat the mixture at a temperature of 800°C to 950°C for a period of 1 to 5 hours. By such heat treatment, a titanium-containing oxide can be obtained. Alternatively, pre-sintering may be performed before the main firing. Pre-sintering is carried out at a temperature of 450°C to 700°C for a period of 5 to 24 hours.

[0052] When using methods that involve water, such as the wet process, attention should be paid to the amount of residual moisture after firing. Residual moisture can react with the aluminum alkoxide compound added in a later stage to form a resistive component. Therefore, adjusting the firing temperature and firing time also contributes to controlling the radial distribution function of Al using FT-EXAFS.

[0053] The sample obtained by the calcination process can be subjected to grinding to break down the aggregates (secondary particles) into primary particles. For example, grinding methods such as mortars, ball mills, sand mills, vibrating ball mills, planetary ball mills, bead mills, jet mills, counter-jet mills, and swirling airflow jet mills can be used. During grinding, wet grinding with liquid grinding aids such as water, ethanol, ethylene glycol, benzene, or hexane can also be used. These grinding aids are effective in improving grinding efficiency and increasing the amount of fine powder produced. A more preferred method is a ball mill using zirconia balls as the media, and wet grinding with a liquid grinding aid is preferred. Furthermore, organic substances such as polyols may be added as grinding aids to improve grinding efficiency. The type of polyol is not particularly limited, but pentaerythritol, triethylolethane, trimethylolpropane, etc., can be used alone or in combination.

[0054] Furthermore, re-calcination may be performed after the grinding process. The average crystallite size of the titanium-containing oxide particles can be controlled by adjusting the calcination conditions. Re-calcination may be performed in air, or in an inert atmosphere using oxygen, nitrogen, argon, etc. Re-calcination should be performed at a temperature of 250°C to 900°C for about 1 minute to 10 hours. If the temperature is below 900°C, sintering between powder particles can be avoided. If the temperature is above 250°C, impurities (organic matter) that adhere during wet grinding can be removed. Preferably, re-calcination is performed at a temperature of 400°C to 700°C for 10 minutes to 3 hours. It is also preferable to wash with an aqueous solvent before re-calcination.

[0055] Furthermore, the particles can be classified as needed to obtain primary particles having a specific particle size.

[0056] Next, an electrode slurry is prepared using the titanium-containing oxide active material prepared as described above. If a second active material other than titanium-containing oxide is to be used, the electrode slurry is prepared using the second active material together with the titanium-containing oxide active material (first active material). Specifically, the active material and conductive agent are mixed to obtain a mixture, and then a binder, an aluminum alkoxide compound, and a solvent are added and kneaded and dispersed to prepare the slurry. For example, N-methylpyrrolidone (NMP) can be used as the solvent (dispersion medium).

[0057] Aluminum alkoxides are a type of metal alkoxide. Metal alkoxides have a structure in which an alkoxy group is coordinated to a central metal element (M: Ti, Zr, Al, Si, etc.), and are classified as M(OR). nThis material is represented by [formula]. It reacts with a Lewis base to synthesize a material with MOM bonds as the main chain. The aluminum alkoxide compound added to the electrode slurry preferably has at least two substituted alkoxy groups, and the other substituents are functional groups with a chain-like or cyclic structure composed of C, O, N, etc. It is even more preferable to have a chelate structure. It is also preferable to use an alkoxide compound having substituents with 3 or more carbon atoms. For example, di-2-butoxyaluminum ethyl acetacetate (Al(C4H9O)2(C6H9O3)), aluminum tri-2-butoxide (Al(OC4H9)3), di-2-butoxyaluminum acetylacetate (Al(C4H9O)2(C5H7O2)), aluminum trisecondary butoxide (Al(O-sec-C4H9)3), etc. can be used. In electrodes to which the above aluminum alkoxide compounds are added, the peak intensity ratio I is measured in the radial distribution function of Al by FT-EXAFS. A / I B The above-described state, where the value is between 3.5 and 9, is easily obtained. In other words, the addition of these aluminum alkoxide compounds is effective in suppressing side reactions on the electrode. Other aluminum alkoxide compounds with fewer than 4 carbon atoms in the substituent include, for example, aluminum isopropoxide (Al(Oi-Pr)3). The added aluminum alkoxide compound may be one type or two or more types.

[0058] Solvents are used with aluminum alkoxide compounds to maintain their structure during storage. Examples of solvents include alcohols such as ethanol, propanol, and butanol. Furthermore, alcohol is released from aluminum alkoxides through hydrolysis. Therefore, even when using aluminum alkoxide reagents with alcohol-free solvents, alcohol is introduced into the system. As described above, aggregates containing the active material are formed by the reaction of alcohol and binders. These aggregates may contain the active material (titanium-containing oxide), the binder, and, for example, aluminum oxide compounds formed by the liberation of organic components of the aluminum alkoxide.

[0059] The amount and size of aggregates formed can be controlled by adjusting the proportions of each component (active material, conductive agent, binder) included in the electrode, as well as the type and amount of aluminum alkoxide compound added. Furthermore, the size of the aggregates can be controlled by adjusting the timing of the addition of the aluminum alkoxide compound.

[0060] For example, reducing the amount of aluminum alkoxide compound added reduces the number of aggregates in the active material-containing layer, resulting in a lower specific S ratio. G / S E The ratio tends to decrease. Conversely, increasing the amount of aluminum alkoxide compound added increases the aggregates in the active material-containing layer, resulting in a decrease in the ratio S. G / S E There is a tendency for this to increase.

[0061] The aluminum alkoxide compound may be added before kneading, or it may be added after kneading and dispersion are complete.

[0062] The slurry prepared as described above is applied to one or both sides of the current collector, and then the coating is dried. In this way, an electrode composite layer (active material-containing layer) can be formed. After that, the electrode composite layer is pressed. In this way, an electrode according to the first embodiment can be obtained.

[0063] <Electrode Measurement> This section describes various measurement methods for electrodes. Specifically, it explains methods for confirming the presence of titanium-containing oxides in the electrodes, methods for cross-sectional observation of electrodes using a scanning electron microscope, and methods for obtaining the radial distribution function by performing a Fourier transform on the EXAFS spectrum obtained from the measurement of the wide-field X-ray absorption fine structure (EXAFS) at the K absorption edge of Al.

[0064] If the electrode to be measured is incorporated into a battery, remove the electrode from the battery as follows: Discharge the battery and disassemble it in a glove box under an inert atmosphere such as an argon atmosphere to remove the electrode. Wash the electrode with diethyl carbonate and then vacuum dry it. This will obtain the measurement sample.

[0065] Confirmation of titanium-containing oxides The active material contained in the electrode can be identified as follows, and the presence or absence of titanium-containing oxides can be confirmed.

[0066] As described above, after cleaning and drying the electrodes removed from the battery, the obtained electrodes are attached to a glass sample plate. At this time, care should be taken to prevent the electrodes from peeling off or lifting by using double-sided tape or similar. If necessary, the electrodes may be cut to an appropriate size for attachment to the glass sample plate. In addition, a Si standard sample may be added to the electrodes to correct the peak position.

[0067] Next, the glass plate with the electrodes attached is placed in a powder X-ray diffraction (XRD) apparatus, and the diffraction pattern is acquired using Cu-Kα rays. Using Cu-Kα rays as the source, the X-ray diffraction pattern can be obtained by changing 2θ within the measurement range of 5° to 90°.

[0068] For powder X-ray diffraction measurements, for example, a SmartLab manufactured by Rigaku will be used. The measurement conditions will be as follows: X-ray source: Cu target Output: 45kV, 200mA Solar slit: 5° for both incident and received light. Step size: 0.02deg Scan speed: 20deg / min Semiconductor detector: D / teX Ultra 250 Sample plate holder: Flat glass sample plate holder (thickness 0.5 mm) Measurement range: 5° ≤ 2θ ≤ 90°.

[0069] If other equipment is used, measurements should be performed using standard Si powder for powder X-ray diffraction to obtain measurement results equivalent to those described above. The conditions under which the peak intensity and peak top position are equivalent to those obtained with the above equipment should be found, and the sample should be measured under those conditions.

[0070] If the active material being measured contains a spinel-type lithium titanium composite oxide, X-ray diffraction measurements can confirm that an X-ray diffraction pattern belonging to the space group Fd-3m can be obtained.

[0071] Next, the sample containing the active material is observed using a scanning electron microscope (SEM). Even during SEM observation, it is desirable to keep the sample from being exposed to air and to perform the observation in an inert atmosphere such as argon or nitrogen.

[0072] Using a 3000x SEM observation image, several particles with primary or secondary particle morphology are selected within the field of view. The selection is made to ensure the particle size distribution is as broad as possible. Energy dispersive X-ray spectroscopy (EDX) is then used to identify the types and composition of the active material elements present in the observed active material particles. This allows for the identification of the types and amounts of elements other than Li present in each selected particle. The same procedure is performed for each of the multiple active material particles to determine their mixing state.

[0073] Next, the active material-containing layer is separated from the current collector using, for example, a spatula, to obtain a powdered electrode mixture sample containing the active material. The collected powdered sample is washed with acetone and dried. The obtained powder is dissolved in hydrochloric acid, the conductive agent is filtered out, and then diluted with deionized water to prepare the measurement sample. The metal content ratio in the measurement sample is calculated using inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0074] If there are multiple types of active materials, their mass ratios are estimated from the elemental content ratios specific to each active material. The ratio of the specific elements to the mass of the active material is determined from the composition of the constituent elements, which is obtained by energy-dispersive X-ray spectroscopy.

[0075] Thus, the active material contained in the electrode can be identified.

[0076] Cross-sectional observation using an electron microscope. As described above, after cleaning and drying the electrodes removed from the battery, cross-sectional milling is performed on the electrodes using an ion milling device. The resulting cross-section is observed with a scanning electron microscope (SEM-EDX) equipped with an energy-dispersive X-ray analyzer. The magnification of the SEM observation is set to 1500x. This observation allows for the identification of the titanium-containing oxide active material in the active material-containing layer.

[0077] Among the active materials containing titanium oxides, primary particle forms and aggregate forms are distinguished as follows. This also allows for the distinction between secondary particles with internal voids and aggregates. The active material and voids in the cross-sectional SEM image of the electrode are subjected to binarization. When binarized, a group of active material that does not contain "0" inside is considered an aggregate. As long as there are no zeros inside, a group of active material with zeros on its outer periphery is also considered an aggregate. An example will be explained with reference to the drawings. Figures 3-5 show conceptual diagrams representing binarized groups of active material.

[0078] In the example shown in Figure 3, there is an isolated 0 inside, so it is not considered an aggregate. Such a cluster could be, for example, a cluster of electrode members that do not form an aggregate, or secondary particles with internal voids. In the examples in Figures 4 and 5, there is no 0 inside, so it is considered an aggregate.

[0079] Among the active materials containing titanium oxides, secondary particles that do not have aluminum oxide compounds on the surface of primary particles located inside the secondary particles and aggregates are distinguished as follows: The electrode cross-section obtained as described above is observed with a transmission electron microscope (TEM-EDX) equipped with an energy-dispersive X-ray analyzer. The magnification for TEM observation is set to 3 million times. In the TEM image of the cross-section of the electrode, aggregates of active material in which the absence of "0"s inside was confirmed in the binarized SEM image as described above, and in which Al can be confirmed to be present inside by EDX, are considered aggregates. Aggregates in which the absence of "0"s inside is confirmed, but Al cannot be confirmed inside, can be judged to be secondary particles without voids, for example, secondary particles formed from primary particles that were not coated with aluminum oxide before becoming secondary particles.

[0080] Based on the identification of aggregated portions and non-aggregated portions in the active material-containing layer in the cross-sectional SEM image of the electrode, the area S of the cross-section of the active material-containing layer is determined. E (Including the cross-sectional area of ​​the aggregates), the total cross-sectional area S of the aggregates G , the least squares circle diameter D of each aggregate g , and the thickness T of the active material-containing layer e Each of these is measured. Using the obtained results, the ratio S G / S E and D g / T e The ratio is calculated. If an active material-containing layer is provided on both the front and back surfaces of the current collector, these ratios are calculated individually for each active material-containing layer on each surface.

[0081] Measurement and Fourier Transform of Broad-Field X-ray Absorption Fine Structure The measurement and Fourier transform of the broad-field X-ray absorption fine structure can be performed as follows.

[0082] After cleaning and drying the electrodes removed from the battery in an inert atmosphere, the sample is introduced into the vacuum chamber of the measuring instrument. The sample is irradiated with X-rays, and the amount of absorption is measured to determine the X-ray absorption fine structure (XAFS) spectrum (electron yield method). In the XAFS spectrum, the broad-spectrum X-ray absorption fine structure, where the structure near the absorption edge appears at an energy level approximately 100 eV or more above the XANES (X-ray Absorption Near Edge Structure) absorption edge, is called EXAFS (Extended X-ray Absorption Fine Structure). Information about the valence and structure of the atom of interest can be obtained from XANES, and in EXAFS analysis, information about the local structure of the sample (atomic species, valence, and distance around the atom of interest) can be obtained by the Fourier transform of the real spectrum (FT-EXAFS; equivalent to the radial distribution function). The obtained spectral data is normalized before and after the absorption edge to derive the XANES spectrum.

[0083] The EXAFS oscillation (χ(k)) obtained from the EXAFS analysis is expressed by the following equation using plane wave simple scattering theory.

[0084]

number

[0085] Here, the subscript i is the number of the configuration circle, S0 2 is the damping factor, N i F is the number of atoms in the i-th coordination sphere. i (k i ) is the backscattering intensity, k i is the wave number, r i σ is the bond distance. i This is the Debye-Waller (DW) factor, φi(k i ) represents a phase shift.

[0086] In general, the number of atoms in each coordination sphere (N i As ) decreases, the amplitude of the EXAFS vibration (χ(k)) decreases. Also, from the above equation, the bond distance (r) with the measured atom decreases. iThe shorter the atom's information, the greater the reflection of that information in the EXAFS vibration (χ(k)).

[0087] k for EXAFS oscillation (χ(k)) 3 The EXAFS function (k) is obtained by applying a weight to enhance the high-wavenumber vibrations. 3 This is the EXAFS function (k 3 By comparing the amplitudes of χ(k), the number of coordination atoms in the measured atom can be estimated.

[0088] In this embodiment, the EXAFS function (k 3 The radial distribution function is obtained by performing a Fourier transform on the EXAFS spectrum of χ(k) in the region 2.5 ≤ k ≤ 7 (corresponding to the EXAFS region). Athena (Non-Patent Literature 1) can be used as the analysis software.

[0089] An example of the radial distribution function obtained by FT-EXAFS for the electrodes in question is shown as a graph in Figure 6.

[0090] The spectrum obtained for the electrode is shown by the solid line 49, and the spectrum obtained for the aluminum alkoxide additive used in the electrode fabrication is shown by the dashed line 90. As shown in Figure 6, the shapes of the two spectra are similar. Therefore, it can be seen that the added aluminum alkoxide exists on the active material on the electrode surface in a form that maintains the Al-O or Al-OC structure, and has not been transformed into other components such as alumina.

[0091] Peak A, in the range of 1.1 Å to 1.5 Å, can be attributed to Al-O bonds. Peak B, in the range of 2.8 Å to 3.2 Å, can be attributed to Al-OC bonds. In electrodes where the Al-OC bonds inherent in elemental aluminum alkoxide are retained on the active material surface without being damaged, side reactions on the active material surface are suppressed.

[0092] The electrode according to the first embodiment contains an active material and an aluminum oxide compound in an active material-containing layer. The active material contains titanium-containing oxide in the form of primary particles and aggregates thereof. The aluminum oxide compound coats the titanium-containing oxide. In the radial distribution function obtained by FT-EXAFS of the K absorption edge of Al for the active material-containing layer, the peak intensity I of peak A appearing in the range of 1.1 Å to 1.5 Å and peak B appearing in the range of 2.8 Å to 3.2 Å are respectively A and I B 3.5 ≤ I A / I B The relationship ≤ 9 is satisfied. The least squares circle diameter D of the aggregate. g The thickness T of the active material-containing layer e It is between 1 / 20 and less than 1 / 2. This electrode can realize a battery with suppressed electrical resistance and resistance rise, and excellent low-temperature performance.

[0093] (Second embodiment) A second embodiment provides a battery comprising a positive electrode, a negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode includes an electrode according to the first embodiment. In a preferred embodiment of the battery, the negative electrode includes an electrode according to the first embodiment.

[0094] The battery may further include a separator positioned between the positive and negative electrodes. The positive electrode, negative electrode, and separator can constitute an electrode group. The electrolyte can be held within the electrode group.

[0095] Furthermore, such a battery may further comprise an outer casing that houses the electrode group and the electrolyte.

[0096] Furthermore, such a battery may further comprise a positive terminal electrically connected to the positive electrode and a negative terminal electrically connected to the negative electrode. At least a portion of the positive terminal and at least a portion of the negative terminal may extend outside the outer casing.

[0097] The battery in question can be, for example, a lithium-ion secondary battery. Further, the battery includes, for example, a non-aqueous electrolyte battery containing a non-aqueous electrolyte as the electrolyte.

[0098] Hereinafter, the negative electrode, positive electrode, electrolyte, separator, exterior member, positive electrode terminal, and negative electrode terminal will be described in detail.

[0099] (1) Negative electrode The negative electrode includes a negative electrode current collector and a negative electrode active material-containing layer (negative electrode composite material layer) carried on one side or both sides of the negative electrode current collector and containing a negative electrode active material, a conductive agent, and a binder.

[0100] The negative electrode can be the electrode according to the first embodiment. In the aspect as the negative electrode, the negative electrode current collector, the negative electrode active material, and the negative electrode active material-containing layer of the negative electrode respectively correspond to the current collector, the active material, and the active material-containing layer of the electrode according to the first embodiment. Since the electrode according to the first embodiment has been described in detail above, the description of the negative electrode here is omitted.

[0101] (2) Positive electrode The positive electrode includes a positive electrode current collector and a positive electrode active material-containing layer (positive electrode composite material layer) carried on one side or both sides of the positive electrode current collector and containing a positive electrode active material, a conductive agent, and a binder.

[0102] The battery according to the second embodiment can include the electrode according to the first embodiment as the positive electrode. Alternatively, the battery can include a positive electrode having a configuration different from that of the electrode according to the first embodiment. Hereinafter, a positive electrode in a mode different from that of the electrode according to the first embodiment will be described.

[0103] As the positive electrode active material, a lithium-containing nickel cobalt manganese oxide (for example, Li w Ni x Co y Mn z O2, where 0 < w ≦ 1 and x + y + z = 1 in the formula; or, Li 1-w [[ID=�8]]Ni 1-x-y-z Co x Mn y M1 zrepresented by O2, wherein M1 is one or more selected from the group consisting of Mg, Al, Si, Ti, Zn, Zr, Ca and Sn, -0.2 < w < 0.5, 0 < x < 0.5, 0 < y < 0.5, 0 ≦ z < 0.1, and x + y + z < 1). In addition, various oxides, for example, lithium-containing cobalt oxides (e.g., LiCoO2), manganese dioxide, lithium manganese composite oxides (e.g., LiMn2O4, LiMnO2), lithium-containing nickel oxides (e.g., LiNi 0.8 Co 0.2 O2), lithium-containing iron oxides, vanadium oxides containing lithium, and chalcogen compounds such as titanium disulfide and molybdenum disulfide may also be included. The type of the positive electrode active material used can be one type or two or more types.

[0104] Examples of the binder include, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide, polyamide, and the like. The type of the binder can be one type or two or more types.

[0105] Examples of the conductive agent include carbon blacks such as acetylene black and ketjen black, graphite, carbon fiber, carbon nanotube, fullerene, and the like. The type of the conductive agent can be one type or two or more types. [[ID=?]]

[0106] [[ID=?]] In the positive electrode active material-containing layer, the mixing ratio of the positive electrode active material, the conductive agent, and the binder is preferably 80% by mass or more and 95% by mass or less for the positive electrode active material, 3% by mass or more and 18% by mass or less for the conductive agent, and 2% by mass or more and 17% by mass or less for the binder.

[0107] It should be noted that there seem to be some formatting or numbering issues in the original text where some consecutive tags like

[0106] and are not clearly related to the content in a typical way. I've translated as accurately as possible based on the provided rules.As the current collector, aluminum foil or aluminum alloy foil is preferred, and its average crystal grain size is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 5 μm or less. A current collector made of aluminum foil or aluminum alloy foil having such an average crystal grain size can dramatically increase strength, making it possible to increase the density of the positive electrode with high pressing pressure, and thereby increasing the battery capacity.

[0108] Aluminum foil or aluminum alloy foil with an average grain size of 50 μm or less is complexly influenced by many factors, including material composition, impurities, processing conditions, heat treatment history, and annealing heating conditions. The diameter is adjusted during the manufacturing process by combining these various factors.

[0109] The thickness of the current collector is preferably 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% or higher. As for the aluminum alloy, an alloy containing elements such as magnesium, zinc, and silicon is preferred. On the other hand, the content of transition metals such as iron, copper, nickel, and chromium is preferably 1% or less.

[0110] The positive electrode is manufactured, for example, by suspending a positive electrode active material, a conductive agent, and a binder in a suitable solvent, applying the resulting slurry to a current collector and drying it to create a positive electrode active material-containing layer, and then pressing it. Alternatively, the positive electrode active material, conductive agent, and binder may be formed into pellets and used as the positive electrode active material-containing layer.

[0111] The positive electrode active material-containing layer preferably has a porosity of 20% to 50%. A positive electrode equipped with such a positive electrode active material-containing layer is high-density and has excellent affinity with the electrolyte. A more preferable porosity is 25% to 40%.

[0112] The density of the positive electrode active material-containing layer is 2.5 g / cm³. 3 It is preferable to make it greater than or equal to the above.

[0113] (3) Electrolyte Examples of electrolytes include liquid non-aqueous electrolytes prepared by dissolving an electrolyte salt (solute) in a non-aqueous solvent, and gel-like non-aqueous electrolytes obtained by compounding a liquid non-aqueous electrolyte with a polymer material.

[0114] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium arsenide hexafluoride (LiAsF6), lithium difluorophosphate (LiPO2F2), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bistrifluoromethylsulfonyliimide [LiN(CF3SO2)2]. These electrolyte salts may be used individually or in combination of two or more types.

[0115] It is preferable to dissolve the electrolyte salt in a non-aqueous solvent at a concentration of 0.5 mol / L to 2.5 mol / L.

[0116] Examples of non-aqueous solvents include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC); linear carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); cyclic ethers such as tetrahydrofuran (THF) and 2-methyl tetrahydrofuran (2MeTHF); linear ethers such as dimethoxyethane (DME); cyclic esters such as γ-butyrolactone (BL); linear esters such as methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate; and organic solvents such as acetonitrile (AN) and sulfolane (SL). These organic solvents can be used individually or as mixtures of two or more.

[0117] Examples of polymer materials used in gel-like non-aqueous electrolytes include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

[0118] (4) Separator The separator is not particularly limited as long as it has insulating properties, but porous films or nonwoven fabrics made of polymers such as polyolefins, cellulose, polyethylene terephthalate, polyimide, polyamide-imide, polyvinylidene fluoride, and vinylon can be used. Inorganic oxides such as alumina, titania, and zirconia can also be used. The separator material may be one type, or two or more types may be used in combination. The separator may also be integrated with the electrode.

[0119] (5) Exterior components The exterior component may be formed from laminate film or made of a metal container. When a metal container is used, the lid may be integrated with the container or be a separate component. The wall thickness of the metal container is preferably 0.5 mm or less, and more preferably 0.2 mm or less. Examples of exterior component shapes include flat, rectangular, cylindrical, coin-shaped, button-shaped, sheet-shaped, and laminated types. The exterior component may be for small batteries mounted in portable electronic devices, as well as for large batteries mounted in two-wheeled or four-wheeled automobiles.

[0120] The thickness of the laminate film exterior component should preferably be 0.2 mm or less. Examples of laminate films include multilayer films containing a resin film and a metal layer placed between the resin films. For weight reduction, the metal layer is preferably aluminum foil or aluminum alloy foil. The resin film can be made of polymer materials such as polypropylene (PP), polyethylene (PE), nylon, or polyethylene terephthalate (PET). The laminate film can be sealed by heat fusion and molded into the shape of the exterior component.

[0121] Metal containers are made from aluminum or aluminum alloys. As aluminum alloys, alloys containing elements such as magnesium, zinc, and silicon are preferred. In aluminum or aluminum alloys, it is preferable to keep the content of transition metals such as iron, copper, nickel, and chromium to 100 ppm or less in order to dramatically improve long-term reliability and heat dissipation in high-temperature environments.

[0122] The metal container made of aluminum or an aluminum alloy preferably has an average crystal grain size of 50 μm or less, more preferably 30 μm or less, and even more preferably 5 μm or less. By setting the average crystal grain size to 50 μm or less, the strength of the metal container made of aluminum or an aluminum alloy can be dramatically increased, making it possible to further thin the container. As a result, it is possible to realize a lightweight, high-output battery with excellent long-term reliability suitable for automotive applications and other uses.

[0123] An example of such a battery will be described with reference to Figures 7 and 8. The flat-type battery shown in Figure 7 comprises a flat-shaped wound electrode group 1, an outer casing member 2, a positive electrode terminal 7, a negative electrode terminal 6, and an electrolyte (not shown). The outer casing member 2 is a bag-shaped outer casing member made of laminate film. The wound electrode group 1 is housed in the outer casing member 2. As shown in Figure 8, the wound electrode group 1 includes a positive electrode 3, a negative electrode 4, and a separator 5, and is formed by spirally winding a laminate made by stacking the negative electrode 4, separator 5, positive electrode 3, and separator 5 from the outside in that order, and then press molding it.

[0124] The positive electrode 3 includes a positive electrode current collector 3a and a positive electrode active material containing layer 3b. The positive electrode active material containing layer 3b contains positive electrode active material. The positive electrode active material containing layer 3b is formed on both sides of the positive electrode current collector 3a. The negative electrode 4 includes a negative electrode current collector 4a and a negative electrode active material containing layer 4b. The negative electrode active material containing layer 4b contains negative electrode active material. The negative electrode active material containing layer 4b is formed on both sides of the negative electrode current collector 4a.

[0125] As shown in Figure 7, near the outer edge of the wound electrode group 1, the positive electrode terminal 7 is connected to the positive electrode 3. The negative electrode terminal 6 is connected to the negative electrode 4 in the outermost layer. Both the positive electrode terminal 7 and the negative electrode terminal 6 extend to the outside through an opening in the outer casing member 2.

[0126] The battery in question is not limited to the configurations shown in Figures 7 and 8, but can also have a configuration like the one shown in Figure 9.

[0127] In the rectangular battery shown in Figure 9, the wound electrode group 11 is housed in a bottomed rectangular cylindrical metal container 12, which serves as the outer casing. A rectangular lid 13 is welded to the opening of the container 12. The flattened wound electrode group 11 may have a configuration similar to that of the wound electrode group 1 described with reference to Figures 7 and 8, for example.

[0128] The negative electrode tab 14 has one end electrically connected to the negative electrode current collector and the other end electrically connected to the negative electrode terminal 15. The negative electrode terminal 15 is fixed to the rectangular cover 13 with a hermetic seal interposed with a glass material 16. The positive electrode tab 17 has one end electrically connected to the positive electrode current collector and the other end electrically connected to the positive electrode terminal 18 fixed to the rectangular cover 13.

[0129] The negative electrode tab 14 is manufactured from a material such as aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, or Si. It is preferable that the negative electrode tab 14 be made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0130] The positive electrode tab 17 is manufactured from a material such as aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, or Si. It is preferable that the positive electrode tab 17 be made of the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0131] Although the illustrated battery uses a wound electrode group in which the separator is wound together with the positive and negative electrodes, a stacked electrode group may also be used in which the separator is folded in a zigzag pattern and the positive and negative electrodes are alternately arranged at the folded sections.

[0132] The battery according to the second embodiment includes the electrodes according to the first embodiment. Therefore, the battery has suppressed electrical resistance and resistance rise, and exhibits excellent low-temperature performance.

[0133] (Third embodiment) According to a third embodiment, a battery pack is provided, which comprises the battery according to the second embodiment.

[0134] The battery pack according to the third embodiment may comprise one or more of the batteries (single cells) according to the second embodiment described above. Multiple batteries that may be included in such a battery pack can be electrically connected to each other in series or parallel to form a battery pack. Such a battery pack may include multiple battery packs.

[0135] Next, an example of a battery pack according to the third embodiment will be described with reference to the drawings.

[0136] Figure 10 is an exploded perspective view of an example battery pack according to the second embodiment. Figure 11 is a block diagram showing the electrical circuit of the battery pack in Figure 10.

[0137] The battery pack 20 shown in Figures 10 and 11 comprises a plurality of individual cells 21. Each individual cell 21 may be a flat-type battery, an example of the second embodiment described with reference to Figure 9.

[0138] Multiple individual cells 21 are stacked so that their outwardly extending negative terminals 51 and positive terminals 61 are aligned in the same direction, and then fastened together with adhesive tape 22 to form a battery pack 23. These individual cells 21 are electrically connected in series with each other, as shown in Figure 11.

[0139] The printed circuit board 24 is positioned opposite the side from which the negative terminal 51 and positive terminal 61 of the single cell 21 extend. As shown in Figure 11, the printed circuit board 24 is equipped with a thermistor 25, a protection circuit 26, and terminals 27 for supplying power to external devices. An insulating plate (not shown) is attached to the side of the printed circuit board 24 that faces the battery pack 23 to avoid unnecessary connections with the wiring of the battery pack 23.

[0140] The positive lead 28 is connected to the positive terminal 61 located at the bottom layer of the battery pack 23, and its tip is inserted into the positive connector 29 of the printed circuit board 24 for electrical connection. The negative lead 30 is connected to the negative terminal 51 located at the top layer of the battery pack 23, and its tip is inserted into the negative connector 31 of the printed circuit board 24 for electrical connection. These connectors 29 and 31 are connected to the protection circuit 26 through wiring 32 and 33 formed on the printed circuit board 24.

[0141] The thermistor 25 detects the temperature of the individual cell 21, and the detection signal is transmitted to the protection circuit 26. The protection circuit 26 can interrupt the positive side wiring 34a and the negative side wiring 34b between the protection circuit 26 and the terminal 27 for supplying power to external devices under predetermined conditions. An example of a predetermined condition is when the temperature detected by the thermistor 25 exceeds a predetermined temperature. Another example of a predetermined condition is when overcharging, over-discharging, overcurrent, etc., of the individual cell 21 is detected. This detection of overcharging, etc., is performed for individual cell 21 or for the entire battery pack 23. When detecting individual cell 21, the battery voltage may be detected, or the positive electrode potential or negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each individual cell 21. In the battery pack 20 of Figures 10 and 11, wiring 35 for voltage detection is connected to each individual cell 21. Detection signals are transmitted to the protection circuit 26 through these wirings 35.

[0142] Protective sheets 36 made of rubber or resin are placed on three sides of the battery pack 23, excluding the side on which the positive terminal 61 and negative terminal 51 protrude.

[0143] The battery pack 23 is housed in a storage container 37 together with each protective sheet 36 and the printed circuit board 24. Specifically, the protective sheets 36 are placed on both inner surfaces in the long direction and on each inner surface in the short direction of the storage container 37, and the printed circuit board 24 is placed on the inner surface opposite to the short direction. The battery pack 23 is located in the space enclosed by the protective sheets 36 and the printed circuit board 24. The lid 38 is attached to the top surface of the storage container 37.

[0144] Alternatively, heat-shrinkable tape may be used instead of adhesive tape 22 to secure the battery pack 23. In this case, protective sheets are placed on both sides of the battery pack, the heat-shrinkable tape is wrapped around it, and then the heat-shrinkable tape is heat-shrinked to secure the battery pack.

[0145] Figures 10 and 11 show a configuration in which the single cells 21 are connected in series, but they may be connected in parallel to increase the battery capacity. Furthermore, assembled battery packs can also be connected in series and / or in parallel.

[0146] Furthermore, the configuration of the battery pack can be appropriately modified depending on the application. Preferably, the battery pack is one that requires good cycle performance when drawing high current. Specific applications include power supplies for digital cameras, and in-vehicle use in two-wheeled or four-wheeled hybrid electric vehicles, two-wheeled or four-wheeled electric vehicles, and electric assist bicycles. Such a battery pack is particularly suitable for in-vehicle use.

[0147] The battery pack according to the third embodiment comprises the battery according to the second embodiment. Therefore, this battery pack has suppressed electrical resistance and resistance rise, and excellent low-temperature performance. [Examples]

[0148] Examples are described below, but the present invention is not limited to the examples listed below, unless it exceeds the spirit of the present invention.

[0149] (Example 1) In Example 1, the non-aqueous electrolyte battery of Example 1 was prepared by following the procedure described below.

[0150] Fabrication of the negative electrode Follow these steps to use Li4Ti5O 12 A lithium titanium composite oxide powder having the following composition and spinel structure was prepared.

[0151] First, titanium dioxide of the anatase type was added to a solution of lithium hydroxide dissolved in pure water, and the mixture was stirred and dried. These raw materials were mixed so that the molar ratio of Li:Ti in the mixture was 4:5.

[0152] The mixed raw materials were calcined at 900°C for 3 hours in an air atmosphere. The calcined material was then ground in a ball mill using zirconia balls as the media, and subsequently washed with water. After heat treatment at 600°C for 30 minutes in an air atmosphere, it was classified. Thus, a powder product was obtained.

[0153] The average primary particle size of the obtained product powder was analyzed by SEM. The results showed that the obtained product powder consisted of primary particulate particles with an average primary particle size of 700 nm. Furthermore, the composition and crystal structure of the obtained product were analyzed using ICP and X-ray diffraction measurements. The results showed that the obtained product had a spinel-type crystal structure and contained Li4Ti5O 12 It was found to be a lithium titanium composite oxide having the following composition. The powder of this product was used as the negative electrode active material.

[0154] Next, carbon as a conductive agent was added to the powder of spinel-type lithium titanium composite oxide as a negative electrode active material, and they were mixed with a Henschel mixer to obtain a mixture. To this mixture, polyvinylidene fluoride (PVdF) as a binder, aluminum alkoxide, and N-methylpyrrolidone (NMP) as a dispersion medium were added, and they were kneaded with a planetary mixer. As the aluminum alkoxide, di-2-butoxyaluminum ethyl acetoacetate was added. At this time, kneading was performed at a relatively high solid content rate (solid kneading), and a relatively strong dispersing force was applied. Then, NMP was further added to adjust to the final solid content rate. Thus, a slurry (slurry for producing a negative electrode) was obtained.

[0155] In the above mixing, the addition amounts of carbon, PVdF, and the aluminum alkoxide compound were adjusted so that the ratio of the negative electrode active material:carbon:PVdF:aluminum alkoxide compound in the obtained slurry was 90 parts by mass:5 parts by mass:4 parts by mass:1 part by mass.

[0156] After mixing with the above planetary mixer, dispersion was performed with a bead mill.

[0157] This slurry was applied to both sides of a current collector made of an aluminum foil with a thickness of 15 μm, and the coating film was dried at 125°C. Next, the dried coating film was subjected to a roll press treatment. Further, vacuum drying was performed for 12 hours in a 90°C environment. Thus, a negative electrode was produced which comprises a current collector and a negative electrode active material-containing layer formed on both surfaces of this current collector and having an electrode density (excluding the current collector) of 2.0 g / cm 3 The thickness of the negative electrode active material-containing layer formed on each surface of the current collector was 40 μm, respectively.

[0158] 《Fabrication of Positive Electrode》 First, lithium nickel cobalt manganese composite oxide (LiNi 0.5 Co 0.3 Mn 0.2A powder of O2 was prepared. 90 parts by mass of positive electrode active material was mixed with 5 parts by mass of acetylene black as a conductive agent in a Henschel mixer to obtain a mixture. Next, 5 parts by mass of PVdF and N-methylpyrrolidone (NMP) were added to this mixture in a fixed ratio and kneaded in a planetary mixer to obtain a slurry. This slurry was applied to both sides of a current collector made of 15 μm thick aluminum foil, and the coating was dried. Furthermore, the dried coating was subjected to a roll press treatment. Thus, the current collector and the electrode formed on both sides of the current collector with an electrode density (excluding the current collector) of 3.0 g / cm³ were obtained. 3 A positive electrode was fabricated comprising a positive electrode active material-containing layer.

[0159] Fabrication of electrode groups Two separators made of porous polyethylene film with a thickness of 20 μm were prepared.

[0160] Next, the previously fabricated positive electrode, one separator, the previously fabricated negative electrode, and another separator were stacked in this order to obtain a laminate. This laminate was then wound into a spiral shape. A group of flattened electrodes was fabricated by heating and pressing this at 90°C.

[0161] The resulting electrode group was placed in a pack made of laminate film and vacuum-dried at 95°C for 12 hours. The laminate film used was constructed by forming polypropylene layers on both sides of aluminum foil.

[0162] Preparation of liquid non-aqueous electrolytes A mixed solvent was prepared by mixing propylene carbonate (PC) and methyl ethyl carbonate (MEC) in a 1:1 volume ratio. A liquid non-aqueous electrolyte was prepared by dissolving LiPF6, the electrolyte, in 1 M solution in this mixed solvent.

[0163] Manufacturing of non-aqueous electrolyte secondary batteries A liquid non-aqueous electrolyte was injected into a laminate film pack containing an electrode group as described above. Subsequently, the pack was completely sealed by heat sealing. Thus, a non-aqueous electrolyte secondary battery having the structures shown in FIGS. 7 and 8 described above was manufactured.

[0164] Next, the manufactured non-aqueous electrolyte secondary battery was charged at a charging rate of 1 A (1 C) in an environment of 25° C. to adjust the state of charge (SOC) to 40%, and then subjected to a heat treatment at 70° C. for 24 hours. Then, the battery cooled to room temperature was discharged at 1 A to 1.5 V in an environment of 25° C., and then charged at 1 A to adjust the SOC to 50%.

[0165] (Example 2) In Example 2, except that in order to control D G / T e aluminum alkoxide was added after dispersion by a bead mill without adding aluminum alkoxide during kneading with a planetary mixer during the production of the negative electrode slurry, a non-aqueous electrolyte battery was manufactured in the same procedure as in Example 1.

[0166] (Example 3) In Example 3, except that the value of S G / S e was controlled to be small by reducing the amount of aluminum alkoxide added to the negative electrode production slurry, a non-aqueous electrolyte battery was manufactured in the same procedure as in Example 1.

[0167] (Example 4) In Example 4, except that D G / T e and S G / S e were controlled, a non-aqueous electrolyte battery was manufactured in the same procedure as in Example 1. For the control of D G / T e the same means as in Example 2 were applied. For S G / S e it was controlled to be small by the same means as in Example 3. <00,00761>

[0168] (Example 5) In Example 5, by increasing the amount of aluminum alkoxide added to the slurry for negative electrode preparation, S G / S e A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the value of was significantly controlled.

[0169] (Example 6) In Example 6, D is as follows: G / T e and S G / S e A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the following was controlled. G / T e The same means as in Example 2 were applied to control S. G / S e This was largely controlled by the same means as in Example 5.

[0170] (Example 7) In Example 7, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the aluminum alkoxide added to the slurry for negative electrode preparation was changed from di-2-butoxyaluminum ethyl acetacetate to aluminum trisec-butoxide.

[0171] (Example 8) In Example 8, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the aluminum alkoxide added to the slurry for negative electrode preparation was changed from di-2-butoxyaluminum ethyl acetacetate to aluminum trisec-butoxide, and the aluminum alkoxide was added after dispersion using a bead mill, rather than during mixing in a planetary mixer.

[0172] (Example 9) In Example 9, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the heat treatment conditions after washing with water during the preparation of the negative electrode active material were changed to adjust the amount of residual moisture. Specifically, the heat treatment temperature was lowered and the heat treatment time was shortened.

[0173] (Example 10) In Example 10, the residual moisture content of the negative electrode active material was adjusted as follows, and D G / T e A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the remaining water content of the negative electrode active material was controlled by the same means as in Example 9. G / T e The same means as in Example 2 were applied to control it.

[0174] (Comparative Example 1) In Comparative Example 1, aluminum alkoxide was not added during the mixing process in the planetary mixer when preparing the negative electrode slurry. Instead, after mixing, a dispersion medium was added to further dilute the aluminum alkoxide, resulting in a low solid content. G / T e A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the following was controlled:

[0175] (Comparative Examples 2 to 4) In Comparative Examples 2 to 4, non-aqueous electrolyte batteries were manufactured using the same procedure as in Example 1, except that the conditions for mixing in the planetary mixer during negative electrode slurry preparation were changed as follows. In all of Comparative Examples 2 to 4, the solid content during mixing was kept relatively low so that the dispersion force during mixing in the planetary mixer was weakened. In Comparative Example 2, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after mixing to a diluted state with a low solid content obtained by adding a dispersion medium. In Comparative Example 4, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after dispersion by bead milling.

[0176] (Comparative Examples 5 to 7) In Comparative Examples 5 to 7, non-aqueous electrolyte batteries were manufactured using the same procedure as in Example 1, except that the conditions for mixing in the planetary mixer during negative electrode slurry preparation were changed as follows. In all of Comparative Examples 5 to 7, the solid content during mixing was increased to enhance the dispersion force during mixing in the planetary mixer. In Comparative Example 5, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after mixing to a diluted state with a low solid content obtained by adding a dispersion medium. In Comparative Example 7, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after dispersion by bead milling.

[0177] (Comparative Example 8) In Comparative Example 8, the aluminum alkoxide added to the slurry for negative electrode preparation was changed from di-2-butoxyaluminum ethyl acetoacetate to methylaluminoxane (MAO)((Al(CH3)O) n A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the formula was changed to [specific component].

[0178] (Comparative Examples 9 and 10) In Comparative Examples 9 and 10, non-aqueous electrolyte batteries were manufactured using the same procedure as in Example 1, except that the aluminum alkoxide added to the slurry for negative electrode preparation and the timing of its addition were changed as follows: In both Comparative Examples 9 and 10, methylaluminoxane (MAO)((Al(CH3)O)) was used instead of di-2-butoxyaluminum ethyl acetacetate. n In Comparative Example 9, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after mixing to further dilute it with a dispersion medium, resulting in a low solid content. In Comparative Example 10, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after dispersion using a bead mill.

[0179] (Comparative Example 11) In Comparative Example 11, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the heat treatment conditions after washing with water during the preparation of the negative electrode active material were changed to adjust the amount of residual moisture. Specifically, the heat treatment temperature was made even lower and the heat treatment time was made even shorter than in Example 9.

[0180] (Comparative Examples 12 and 13) In Comparative Examples 12 and 13, non-aqueous electrolyte batteries were manufactured using the same procedure as in Example 1, except that the residual moisture content of the negative electrode active material was adjusted as follows, and the timing of adding aluminum alkoxide to the slurry for negative electrode preparation was changed as follows. The residual moisture content of the negative electrode active material was controlled by the same means as in Comparative Example 11. In Comparative Example 12, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after mixing to dilute it with a dispersion medium to a low solid content. In Comparative Example 13, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after dispersion using a bead mill.

[0181] (Comparative Example 14) In Comparative Example 14, by significantly reducing the amount of aluminum alkoxide added to the slurry for negative electrode preparation, S G / S e A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the value of was controlled to be significantly smaller.

[0182] (Comparative Examples 15 and 16) In Comparative Examples 15 and 16, the amount of aluminum alkoxide added to the slurry for negative electrode preparation was significantly reduced, resulting in S G / S e A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the value of was controlled to be significantly smaller and the timing of alkoxide addition was changed as follows. In Comparative Example 15, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after mixing to dilute it with a dispersion medium to a low solid content. In Comparative Example 16, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after dispersion using a bead mill.

[0183] (Comparative Example 17) In Comparative Example 17, by significantly increasing the amount of aluminum alkoxide added to the slurry for negative electrode preparation, S G / S e A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the value of was significantly controlled.

[0184] (Comparative Examples 18 and 19) In Comparative Examples 18 and 19, the amount of aluminum alkoxide added to the slurry for negative electrode preparation was significantly increased, resulting in S G / S e A non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the value of was significantly controlled and the timing of its addition was changed as follows. In Comparative Example 18, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after mixing to dilute it with a dispersion medium to a low solid content. In Comparative Example 19, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after dispersion using a bead mill.

[0185] (Comparative Example 20) In Comparative Example 20, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the addition of aluminum alkoxide to the slurry for negative electrode preparation was omitted, and the solid content during mixing was kept relatively low so that the dispersion force during mixing in a planetary mixer was weakened.

[0186] (Comparative Example 21) In Comparative Example 21, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the addition of aluminum alkoxide to the slurry for negative electrode preparation was omitted.

[0187] (Comparative Example 22) In Comparative Example 22, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the addition of aluminum alkoxide to the slurry for negative electrode preparation was omitted, and the solid content during mixing was increased to enhance the dispersion force when mixing in a planetary mixer.

[0188] (Comparative Example 23) In Comparative Example 23, a non-aqueous electrolyte battery was manufactured using the same procedure as in Example 1, except that the negative electrode active material was granulated into secondary particles before being used in the slurry for negative electrode preparation. Primary particulate lithium titanium composite oxide powder, used as the negative electrode active material, was subjected to granulation using a spray dryer to obtain secondary particles.

[0189] (Comparative Examples 24 and 25) In Comparative Examples 24 and 25, non-aqueous electrolyte batteries were manufactured using the same procedure as in Example 1, except that the negative electrode active material was secondarily granulated before being used in the slurry for negative electrode preparation, similar to Comparative Example 23, and the timing of aluminum alkoxide addition was changed as follows. In Comparative Example 24, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after mixing to dilute it with a dispersion medium to a low solid content. In Comparative Example 25, aluminum alkoxide was not added during mixing in the planetary mixer, but was added after dispersion using a bead mill.

[0190] Tables 1 and 2 below summarize the conditions for anode fabrication in the production of non-aqueous electrolyte batteries in Examples 1 to 10 and Comparative Examples 1 to 25. Specifically, Table 1 shows the conditions for heat treatment performed after water washing following ball mill grinding when synthesizing titanium-containing oxide as a negative electrode active material, as well as the form of the titanium-containing oxide powder (primary or secondary particles) when mixed with the slurry for anode fabrication. Table 2 shows the aluminum alkoxide added to the slurry for anode fabrication, the amount of Al (in mg equivalent) relative to the amount of Ti (in mg equivalent) in the slurry depending on the amount of aluminum alkoxide added, the timing of adding the aluminum alkoxide to the slurry for anode fabrication, and the dispersion strength during mixing (solid mixing) with a planetary mixer.

[0191] [Table 1]

[0192] [Table 2]

[0193] <Measurement> For each non-aqueous electrolyte battery manufactured as described above, the negative electrode was analyzed using the FT-EXAFS method described earlier. Peak A in the range of 1.1 Å to 1.5 Å and peak B in the range of 2.8 Å to 3.2 Å were identified in the obtained radial distribution function, and the intensity ratio I between these peaks was determined. A / I B The following was calculated. The results are shown in Table 3 below.

[0194] In addition, SEM observation of the negative electrode cross-section was performed using the method described above. In the obtained cross-sectional SEM image, the area S of the cross-section of the negative electrode active material-containing layer was obtained. E , Total cross-sectional area S of the aggregate G , the average least squares circle diameter D of each aggregate g , and the thickness T of the active material-containing layer e Each was measured, and the ratio S G / S E and D g / T e The following was calculated. The calculated ratios are shown in Table 3 below.

[0195] <Rating> The performance of each non-aqueous electrolyte battery manufactured in Examples 1 to 10 and Comparative Examples 1 to 25 was evaluated as follows. Specifically, the high-current performance and lifespan performance of each battery were evaluated.

[0196] (Large current performance) To confirm the initial resistance of the battery, its high-current performance under low-temperature conditions was evaluated by measuring the low-temperature output resistance as described below.

[0197] First, the battery was charged in a 25°C constant temperature bath at a charge rate of 600mA (1C) until the battery voltage reached 2.7V. Then, it was charged at a constant voltage until the current value reached 30mA, followed by a 10-minute rest period. Next, it was discharged at a constant current of 120mA to 1.5V. The discharge capacity obtained at this time was measured.

[0198] Next, it was charged at a charging rate of 600 mA (1C) until the battery voltage reached 2.7V, then charged at a constant voltage until the current value reached 30 mA, and then 50% of the discharge capacity was discharged.

[0199] After that, the temperature of the thermostat was set to -20°C, and the battery was left to standby in the thermostat for 3 hours. The voltage change when the battery was discharged at a constant current of 6A for 10 seconds in a low-temperature (-20°C) thermostat was measured. The value calculated by dividing the voltage change during the 10-second discharge under low-temperature conditions by the current value was defined as the low-temperature output resistance.

[0200] (Life performance) The life performance of the battery was evaluated by measuring the resistance increase in a calendar test under low-temperature conditions as follows.

[0201] After charging the battery so that the state of charge (SOC) was 50%, it was stored in a thermostat set at 85°C for 3 weeks. Then, the resistance increase rate was measured by the following method.

[0202] The battery was taken out of the 85°C thermostat and left to stand in a room-temperature environment until the battery temperature reached room temperature. Subsequently, the battery was placed in a 25°C thermostat, discharged at 600 mA until 1.5V, and then a 10-minute rest period was provided. It was charged at 1A until 2.7V, and the battery was charged at a constant voltage until the current value reached 30 mA at 2.7V. Then, a 10-minute rest period was provided. Next, it was discharged at a constant current of 120 mA until 1.5V. The discharge capacity obtained at this time was measured and defined as the recovery capacity. Then, the capacity corresponding to 50% of the recovery capacity was charged at 600 mA. The temperature of the thermostat was set to -20°C, and after the battery was left to standby in the thermostat for 3 hours, it was discharged at 6A for 10 seconds. The discharge resistance during the 10C discharge for 10 seconds was measured.

[0203] The ratio of the discharge resistance measured after storage to the discharge resistance measured before storage was calculated and defined as the resistance increase rate.

[0204] (Volume energy density) The energy density per unit volume of the battery was evaluated as follows.

[0205] To confirm the volume energy density of the battery, the discharge capacity of the cell was measured.

[0206] First, the battery was charged at a constant current of 600 mA (1C) in a thermostat at 25°C until the battery voltage reached 2.7 V, and then charged at a constant voltage until the current value reached 30 mA. After that, a rest period of 10 minutes was provided. Then, it was discharged at a constant current of 120 mA until 1.5 V. The discharge capacity obtained at this time was measured.

[0207] The volume energy density was calculated by dividing the value obtained by multiplying the discharge capacity by the average operating voltage by the volume of the cell.

[0208] Table 3 below summarizes the results of performance evaluations for each non-aqueous electrolyte battery manufactured in Examples 1 to 10 and Comparative Examples 1 to 25. As the results of the performance evaluations, the evaluation results of the low-temperature output resistance (high-current performance), the resistance increase rate during high-temperature storage (life performance), and the energy density per unit volume described above are shown as relative values with respect to the measured value for Comparative Example 21 taken as the reference value of 100%. In Table 3, the ratio I A / I [[ID=**19**]] B 、S G / S E 、及びD g [[ID=2**6**]] / T <0**000145**>also shown.

[0209]

Table 3

[0210] In Examples 1 to 10, values of D g / T e within the range of 1 / 20 or more and less than 1 / 2 were obtained. In these Examples 1 to 10, it is presumed that good characteristics were obtained because the aggregation was not large and was of an appropriate size. For example, like the difference in manufacturing conditions between Example 1 and Example 2, due to the timing of addition of aluminum alkoxide, D Note: There seems to be a minor formatting issue in the original Japanese text where the tags B and e are not correctly formatted in the English sentence structure. I've tried to maintain the closest possible representation while adhering to the rules. If this is a critical error, more clarification on the text structure might be needed.g / T e Although attempts were made to control the timing of aluminum alkoxide addition, as shown in Table 3, no effect was observed when changing the timing of aluminum alkoxide addition between solid mixing using a planetary mixer and dispersion using a bead mill.

[0211] In contrast, in Comparative Example 1, aluminum alkoxide was added to a low solid content state after further dilution by adding a dispersion medium after kneading, which reduced the reaction frequency between the aluminum alkoxide and the negative electrode active material. Some of the aluminum alkoxide that did not react with the negative electrode active material reacted only with the binder contained in the negative electrode mixture. It is presumed that the reaction product with the binder became a resistor, resulting in inferior high-current performance compared to Example 1.

[0212] In Comparative Examples 2, 3, and 4, weaker dispersion was applied compared to Example 1. Because the dispersion was insufficient, D g / T e As indicated by the fact that the amount increased to more than half, aggregation increased significantly. Due to insufficient dispersion, the aluminum alkoxide was not uniformly dispersed on the surface of the negative electrode active material, resulting in uneven coating of the aluminum alkoxide. The aggregated negative electrode active material was coated, but the negative electrode active material that remained as primary particles was not. It is presumed that the resistance increase rate was inferior to that of Example 1 because of the presence of uncoated negative electrode active material.

[0213] In Comparative Examples 5, 6, and 7, a stronger dispersion was applied compared to Example 1. It is presumed that the excessive dispersion resulted in smaller aggregates, leading to inferior high-current performance compared to Example 1.

[0214] In comparative examples 8, 9, and 10, the ratio I obtained from the FT-EXAFS of Al for the negative electrode was A / I B The value was low. Methylaluminoxane ((Al(CH3)O) added to the negative electrode in Comparative Examples 8, 9, and 10 n In this case, it is presumed that the effect was not obtained because Al-OC bonds were not formed on the surface of the active material, resulting in it becoming a resistor.

[0215] In comparative examples 11, 12, and 13, the ratio I obtained from the FT-EXAFS of Al for the negative electrode was A / I B The value was high. It is presumed that in Comparative Examples 11, 12, and 13, the heat treatment conditions after water washing were kept moderate during the preparation of the negative electrode active material (spinel structure lithium titanate), resulting in a larger amount of residual moisture, which led to the excessive formation of aluminum alkoxide-derived components on the surface of the active material. The formed alkoxide-derived components contained hydrolysis reaction products of aluminum alkoxide, and it is presumed that these hydrolysis reaction products acted as resistors, resulting in inferior high-current performance compared to Example 1. Furthermore, although coated, it is presumed that residual moisture caused side reactions, worsening the resistance increase.

[0216] In Comparative Examples 14, 15, and 16, the amount of aluminum alkoxide solution added was reduced. As the amount of alcohol component in the aluminum alkoxide solution also decreased, the amount of reactants produced by the reaction with the binder also decreased, S G / S E and D g / T e As indicated by the small values ​​of both factors, the amount of aggregates decreased, which is presumed to have resulted in poor high-current performance. Furthermore, it is presumed that the coating on the surface of the negative electrode active material was insufficient, leading to side reactions with the electrolyte and resulting in poor lifespan performance.

[0217] In Comparative Examples 17, 18, and 19, the amount of aluminum alkoxide solution added was increased. As the amount of alcohol component in the aluminum alkoxide solution also increased, the amount of reactants produced by the reaction with the binder also increased, S G / S E and D g / T e As indicated by the large size of both parameters, the amount of aggregates increased. The formation of numerous large aggregates made dense packing impossible, resulting in a decrease in electrode density and energy density.

[0218] In Comparative Examples 20, 21, and 22, since no aluminum alkoxide solution was added, aggregates resulting from the reaction between the alcohol component in the aluminum alkoxide solution and the binder were not formed, which is presumed to be why the high-current performance was inferior to that of Example 1. Furthermore, since there was no coating of the negative electrode active material surface with aluminum alkoxide, it is presumed that the lifespan performance was also inferior.

[0219] In Comparative Examples 23, 24, and 25, secondary lithium titanate powder was used instead of primary lithium titanate powder. Because the secondary particles could not be coated with aluminum alkoxide, no reaction products with the binder were formed, and therefore no resistors were present, resulting in improved output resistance. However, it is presumed that the lifespan performance was inferior because the secondary particles could not be coated with aluminum alkoxide. Furthermore, because the particle size was already large before alkoxide addition, aggregate formation increased. The formation of numerous large aggregates made dense packing impossible, leading to a decrease in electrode density and energy density.

[0220] According to the one or more embodiments and examples described above, an electrode is provided comprising an active material containing a titanium-containing oxide and an active material-containing layer containing an aluminum oxide compound on the surface of the titanium-containing oxide. The form of the titanium-containing oxide includes both primary particles and aggregates containing multiple primary particles. In addition, the FT-EXAFS radial distribution function of Al for the active material-containing layer includes a peak A in the range of 1.1 Å to 1.5 Å and a peak B in the range of 2.8 Å to 3.2 Å, with the peak intensity of peak B being I B Peak intensity I of peak A A Ratio I A / I B The value is between 3.5 and 9. The least squares circle diameter D of the aggregate. g The thickness T of the active material-containing layer e It is between 1 / 20 and less than 1 / 2. This electrode suppresses electrical resistance and resistance rise, enabling the realization of batteries and battery packs with excellent low-temperature performance.

[0221] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and the equivalent scope thereof.

[0222] Several embodiments according to the present invention are appended below. [1] An active material layer comprising an active material containing a titanium-containing oxide and an aluminum oxide compound present on the surface of the titanium-containing oxide, wherein the form of the titanium-containing oxide includes the form of primary particles and the form of aggregates containing a plurality of the primary particles, and in the radial distribution function obtained by Fourier transform of the extended X-ray absorption fine structure spectrum at the K absorption edge of Al for the active material layer, a peak A appearing in the range of 1.1 Å or more and 1.5 Å or less and a peak B appearing in the range of 2.8 Å or more and 3.2 Å or less are included, and the peak intensity I of the peak B B with respect to the peak intensity I of the peak A A of ratio I A / I B has a value of 3.5 or more and 9 or less, and the least-squares circle diameter D of the aggregate g is 1 / 20 or more and less than 1 / 2 with respect to the thickness T of the active material layer e , an electrode. [2] The ratio S of the cross-sectional area S of the aggregate occupying the cross-section with respect to the cross-sectional area S of the active material layer E where the cross-sectional area S of the aggregate occupying the cross-section G is 1 / 200 or more and 1 / 4 or less, the electrode according to [1]. G / S E is 1 / 200 or more and 1 / 4 or less, the electrode according to [1]. [3] The electrode according to [1] or [2], wherein the titanium-containing oxide contains lithium titanate having a spinel structure. [4] A battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode includes the electrode according to any one of [1] to [3]. [5] A battery pack comprising the battery according to [4]. [Explanation of Symbols]

[0223] 1...Electrode group, 2...Outer casing, 3...Positive electrode, 3a...Positive electrode current collector, 3b...Positive electrode active material containing layer, 4...Negative electrode, 4a...Negative electrode current collector, 4b...Negative electrode active material containing layer, 4c...Negative electrode current collector tab, 4d...Aggregate, 5...Separator, 6...Negative electrode terminal, 7...Positive electrode terminal, 11...Electrode group, 12...Container, 13...Rectangular lid, 14...Negative electrode tab, 16...Glass material, 17...Positive electrode tab, 18...Positive electrode terminal, 20...Battery pack, 21...Single cell, 22...Adhesive 1. Adhesive tape, 23. Battery pack, 24. Printed circuit board, 25. Thermistor, 26. Protection circuit, 27. Terminal for supplying power to external devices, 28. Positive lead, 29. Positive connector, 30. Negative lead, 31. Negative connector, 32. Wiring, 33. Wiring, 34a. Positive wiring, 34b. Negative wiring, 35. Wiring, 36. Protective sheet, 37. Storage container, 38. Lid, 51. Negative terminal, 61. Positive terminal.

Claims

1. The active material-containing layer comprises an active material containing a titanium-containing oxide and an aluminum oxide compound on the surface of the titanium-containing oxide, wherein the titanium-containing oxide is in the form of primary particles and in the form of aggregates containing a plurality of such primary particles. The radial distribution function obtained by the Fourier transform of the broad X-ray absorption fine structure spectrum of Al at the K absorption edge for the active material-containing layer includes a peak A appearing in the range of 1.1 Å to 1.5 Å and a peak B appearing in the range of 2.8 Å to 3.2 Å, wherein the peak intensity of peak B is I B Peak intensity I of peak A A Ratio I A / I B The value is between 3.5 and 9, The least squares circle diameter D of the aggregate ｇ The thickness T of the active material-containing layer is ｅ An electrode that is 1 / 20 or more but less than 1 / 2 of the given value.

2. The area S of the cross-section of the active material-containing layer Ｅ The cross-sectional area S of the aggregate occupying the cross-section with respect to Ｇ The ratio S Ｇ / S Ｅ is 1 / 200 or more and 1 / 4 or less, The electrode according to claim 1

3. The electrode according to claim 1, wherein the titanium-containing oxide comprises lithium titanate having a spinel structure.

4. Positive electrode and, The negative electrode and, It is equipped with electrolytes, A battery wherein the negative electrode includes the electrode described in any one of claims 1 to 3.

5. A battery pack comprising the battery described in claim 4.

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