Active material, positive electrode active material for nonaqueous electrolyte secondary batteries, electrode mixture, battery, and method for producing active material

Abstract

This active material has a core part and a coating part that is positioned on the surface of the core part. The core part contains a spinel composite oxide that contains elemental Li, elemental Ni, elemental Mn, and elemental Ti. The molar ratio Ti / (Li + Ni + Mn + Ti) in the core part is 0.05 to 0.15 inclusive. The coating part contains an Al oxide. The content of elemental Al in the active material is 0.020 mass% to 0.100 mass% inclusive. The specific surface area of the active material is 0.5 m2 / g to 2.0 m2 / g inclusive. In the X-ray diffraction pattern of the active material, when IA is the peak intensity of a peak observed at 2θ = 44.2 ± 0.5° and IB is the peak intensity of a peak observed at 2θ = 18.7 ± 0.5°, IA / IB is 0.30 to 0.46 inclusive.

Description

Active material, positive electrode active material for nonaqueous electrolyte secondary battery, electrode mixture, battery, and method for producing active material 【0001】 This invention relates to an active material, a positive electrode active material for a non-aqueous electrolyte secondary battery, an electrode mixture, and a battery. Furthermore, this invention relates to a method for producing the active material. 【0002】 Batteries, which consist of a positive electrode, a negative electrode, and an electrolyte, are widely used as power sources for portable electronic devices such as laptop computers and mobile phones. In recent years, CO2 ２ Secondary batteries are attracting attention as an initiative to prevent global warming through reduction, and various developments are underway to improve their performance. 【0003】 Lithium manganese oxide having a spinel-type structure is known as an active material to be included in the positive electrode of such secondary batteries. For example, Non-Patent Document 1 describes LiNi ０．５ Mn １．３ Ti ０．２ O ４ A spinel-type composite oxide having the compositional formula represented by is described. 【0004】 Incidentally, batteries using a 5V-class spinel-type composite oxide with an operating potential of 4.5V or higher based on a metallic lithium reference potential as the positive electrode active material tend to generate a large amount of gas within the battery due to the reaction between the active material and the electrolyte, which increases the internal pressure of the battery. Therefore, from the perspective of improving battery safety, there is a demand to reduce the amount of gas generated. 【0005】 To reduce the amount of gas generated inside a battery, one can, for example, coat the active material to suppress the reaction between the active material and the electrolyte. 【0006】 International Publication No. 2022 / 259755 brochure 【0007】 Electrochimica Acta 455, 2023, 142425 【0008】In a coated active material, the output characteristics of a battery may be impaired due to the coating portion located on the surface of the active material. Therefore, there is a demand to maintain high output characteristics while reducing the amount of gas generation. The applicant of the present application has previously proposed an active material including a core portion containing a spinel-type composite oxide and a coating portion containing an element such as zirconium (Zr) (Patent Document 1). Although the battery obtained by using the active material described in Patent Document 1 has excellent performance, the suppression of the amount of gas generated from the battery has not been studied. 【0009】 Therefore, an object of the present invention is to provide an active material used for manufacturing a battery having high output characteristics and a low gas generation amount. 【0010】 The present invention relates to an active material having a core portion and a coating portion located on the surface of the core portion, wherein the core portion includes a spinel-type composite oxide containing lithium (Li) element, nickel (Ni) element, manganese (Mn) element, and titanium (Ti) element, and in the core portion, the molar ratio Ti / (Li+Ni+Mn+Ti) of the content of titanium (Ti) element to the total content of lithium (Li) element, nickel (Ni) element, manganese (Mn) element, and titanium (Ti) element is 0.030 or more and 0.10 or less, the coating portion includes an oxide of aluminum (Al), the content of aluminum (Al) element in the active material is 0.020% by mass or more and 0.100% by mass or less, the specific surface area of the active material is 0.5 m ２ / g or more and 2.0 m ２ / g or less, and in the X-ray diffraction pattern of the active material measured by an X-ray diffractometer using CuKα1 line, when the peak intensity of the peak observed at 2θ = 44.2 ± 0.5° is I Ａ , and the peak intensity of the peak observed at 2θ = 18.7 ± 0.5° in the X-ray diffraction pattern is I Ｂ , the value I Ｂ of I Ａ to I Ａ / I Ｂ is 0.30 or more and 0.46 or less. The present invention provides an active material. 【0011】The present invention also provides a method for producing the active material, wherein a coating portion containing aluminum (Al) oxide is formed on the surface of the core portion containing a spinel-type composite oxide containing lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements by atomic deposition. 【0012】 The present invention will be described below based on its preferred embodiments. The active material of the present invention has a core portion and a coating portion. The coating portion is located on the surface of the core portion. The core portion and the coating portion will be described below. 【0013】 [Core] The core is the part that makes up the majority of the active material and serves as the base material for the active material. The core contains at least lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti). From the viewpoint of further improving the output characteristics of a battery incorporating the active material of the present invention, it is preferable that the core of the active material contains Ti in a specific proportion. Specifically, the molar ratio Ti / (Li+Ni+Mn+Ti) of the Ti content to the total content of Li, Ni, Mn, and Ti in the core is preferably 0.030 or higher, more preferably 0.050 or higher, and even more preferably 0.060 or higher. Furthermore, from the viewpoint of maintaining the crystal structure of the active material and further improving the output characteristics of the battery, the molar ratio Ti / (Li+Ni+Mn+Ti) is preferably 0.100 or lower, more preferably 0.080 or lower, and even more preferably 0.070 or lower. 【0014】From the viewpoint of increasing the capacity of a battery incorporating the active material of the present invention, the molar ratio Li / (Li+Ni+Mn+Ti) of the content of Li element to the total content of Li, Ni, Mn, and Ti elements in the core is preferably 0.300 or higher, more preferably 0.330 or higher, and even more preferably 0.340 or higher. Furthermore, from the viewpoint of ensuring a sufficient amount of transition metal elements that are oxidized or reduced during charging and discharging, and thereby ensuring the capacity of a battery incorporating the active material of the present invention, the molar ratio Li / (Li+Ni+Mn+Ti) is preferably 0.400 or lower, more preferably 0.370 or lower, and even more preferably 0.360 or lower. 【0015】 From the viewpoint of increasing the capacity of a battery incorporating the active material of the present invention, the molar ratio Ni / (Li+Ni+Mn+Ti) of the Ni element content to the total content of Li, Ni, Mn, and Ti elements in the core portion is preferably 0.100 or higher, more preferably 0.120 or higher, and even more preferably 0.130 or higher. Furthermore, from the viewpoint of improving the output characteristics of a battery incorporating the active material of the present invention, the molar ratio Ni / (Li+Ni+Mn+Ti) is preferably 0.200 or lower, more preferably 0.170 or lower, even more preferably 0.150 or lower, and particularly preferably 0.145 or lower. 【0016】 From the viewpoint of making it easier to maintain the spinel-type crystal structure, the molar ratio Mn / (Li+Ni+Mn+Ti) of the content of Mn element to the total content of Li, Ni, Mn, and Ti elements in the core is preferably 0.400 or higher, more preferably 0.430 or higher, and even more preferably 0.440 or higher. Also, from the same viewpoint, the molar ratio Mn / (Li+Ni+Mn+Ti) is preferably 0.500 or lower, more preferably 0.470 or lower, and even more preferably 0.460 or lower. 【0017】 The core part is the general formula Li ｘ M ３－ｘ O ４－δThe material contains a spinel-type composite oxide represented by the following general formula: In the above general formula, M represents a metallic element other than lithium (Li). Details of the M element will be described later. From the viewpoint of ensuring the amount of lithium ions that contribute to charging and discharging, it is preferable that x in the above general formula is 0.9 or more. Furthermore, from the viewpoint of increasing the charge-discharge capacity of the active material and the capacity of the battery made using it by ensuring the amount of transition metals among the M elements that are oxidized or reduced during charging and discharging, it is preferable that x is 1.2 or less. In the above general formula, δ represents oxygen deficiency and is preferably 0.0 or more and 0.5 or less. By using the spinel-type composite oxide represented by the above general formula, a battery incorporating the active material of the present invention has a voltage of 4.5V or more (vsLi / Li ＋ The operating potential is as follows. Preferably, the spinel-type composite oxide contained in the core contains nickel (Ni) and manganese (Mn) as M elements in addition to lithium (Li) element. By using a spinel-type composite oxide containing such elements, the output characteristics of a battery incorporating the active material of the present invention containing the spinel-type composite oxide, i.e., the high-rate charge and discharge characteristics, can be improved. 【0018】 Furthermore, it is preferable that the spinel-type composite oxide contained in the core part contains titanium (Ti) as the M element. By including Ti in the spinel-type composite oxide, the output characteristics of the battery incorporating the active material of the present invention containing the spinel-type composite oxide can be further improved and the amount of gas generated can be reduced. 【0019】The spinel-type composite oxide contained in the core may contain one or more elements other than Ni, Mn, and Ti as the M element. When there are two or more other elements, it is preferable that at least one of them is selected from the group consisting of Co and Fe (hereinafter referred to as "M1 element"). The M1 element is a substitution element that mainly contributes to achieving an operating potential of 3.0 V or higher with metallic Li as the reference potential. The other element is preferably an M2 element consisting of one or more elements selected from the group consisting of Na, Mg, Al, P, K, Ca, V, Cr, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce. The M2 element is a substitution element that mainly contributes to stabilizing the crystal structure and improving its properties. The M1 and M2 elements contained in the spinel-type composite oxide are different elemental species. Furthermore, if the spinel-type composite oxide contains only one of the aforementioned other elements, it is preferable that the aforementioned other element is selected from the group consisting of the elements exemplified as M1 and M2. 【0020】 The spinel-type composite oxide contained in the core has the composition formula Li ｘ [Ni ｙ Mn ｚ Ti ３－ｘ－ｙ－ｚ ]O ４－δ It is preferable that it be represented as follows. In the above composition formula, δ represents oxygen deficiency and is preferably 0.0 or more and 0.5 or less. In the above composition formula, x is preferably 0.90 or more, more preferably 1.01 or more, and even more preferably 1.03 or more, from the viewpoint of ensuring the amount of lithium ions that contribute to charging and discharging and increasing the capacity of the battery incorporating the active material of the present invention. Furthermore, from the viewpoint of ensuring a sufficient amount of transition metal elements that are oxidized or reduced during charging and discharging and ensuring the capacity of the battery incorporating the active material of the present invention, x is preferably 1.20 or less, more preferably 1.10 or less, and even more preferably 1.08 or less. 【0021】In the above compositional formula, y is preferably 0.30 or more, more preferably 0.35 or more, and even more preferably 0.39 or more, from the viewpoint of increasing the capacity of the battery incorporating the active material of the present invention. Furthermore, from the viewpoint of improving the output characteristics of the battery incorporating the active material of the present invention, y is preferably 0.60 or less, more preferably 0.50 or less, and even more preferably 0.45 or less. 【0022】 In the above compositional formula, z is preferably 1.20 or higher, more preferably 1.28 or higher, and even more preferably 1.32 or higher, from the viewpoint of easily maintaining the spinel structure. Also, from the same viewpoint, z is preferably 1.50 or lower, more preferably 1.42 or lower, and even more preferably 1.38 or lower. 【0023】 In the above compositional formula, the molar ratio of Ti (3-x-y-z) is preferably 0.10 or higher, more preferably 0.15 or higher, and even more preferably 0.18 or higher, from the viewpoint of further improving the output characteristics of the battery incorporating the active material of the present invention. From a similar viewpoint, the molar ratio of Ti (3-x-y-z) is preferably 0.30 or lower, more preferably 0.25 or lower, and even more preferably 0.22 or lower. 【0024】 The core portion may contain components other than the spinel-type composite oxide described above. However, from the viewpoint of effectively obtaining the properties of the spinel-type composite oxide, it is preferable that the core portion consists of 80% by mass or more of the spinel-type composite oxide, more preferably 90% by mass or more, and more preferably 95% by mass or more (including 100% by mass). 【0025】[Coating] The coating is positioned on the surface of the core and covers the surface of the core. The coating may cover the entire surface of the core, or it may cover a part of the surface of the core. That is, the coating either evenly covers the surface of the core, or partially covers the surface so that a part of the surface of the core is exposed. Considering the purpose of positioning the coating, which is to prevent a decrease in the performance of the core, it is preferable that the coating evenly covers the surface of the core and that the surface of the core is exposed as little as possible. The coverage rate of the coating over the entire surface of the core is preferably 60% or more, more preferably 70% or more, particularly preferably 80% or more, and even more preferably 90% or more. The coverage rate of the coating can be confirmed, for example, by observing the surface of the active material using a scanning transmission electron microscope (STEM) and, if necessary, energy-dispersive X-ray analysis (EDS), or by Auger electron spectroscopy. To increase the coverage rate of the coating, it is advantageous to form the coating by, for example, the atomic deposition method described later. 【0026】 The coating portion is used to improve the output characteristics of the battery incorporating the active material of the present invention and to reduce gas generation. For this purpose, the coating portion preferably contains aluminum (Al) oxide. The general formula for aluminum oxide is AlO ｘ It is represented as, specifically, Al ２ O ３ AlO, Al ２ Examples include O. These aluminum oxides can be used individually or in combination of two or more. The aluminum oxides may be crystalline or amorphous. From the viewpoint of more effectively obtaining the above-mentioned effects obtained by providing a coating, the above formula AlO ｘ In this case, x is preferably greater than 0 and less than or equal to 1.5. The coating may, in some cases, contain oxides of metals other than aluminum in addition to aluminum oxide. Zirconium is an example of a metal other than aluminum. However, when the coating is formed by the atomic deposition method described later, it is preferable that the coating consists only of aluminum oxide and unavoidable impurities. 【0027】 In detail, when a battery equipped with a positive electrode containing an active material containing metal elements such as Mn is repeatedly charged and discharged, the metal elements such as Mn that constitute the active material tend to dissolve into the electrolyte in an ionic state. When metal ions dissolve into the electrolyte, metals such as Mn may precipitate on the negative electrode, which can result in a decrease in the battery's output characteristics. In addition, the amount of gas generated within the battery may increase due to the dissolution of such metal elements. In contrast, since the coating portion is arranged on the surface of the core material particles of the active material of the present invention, the dissolution of metal ions into the electrolyte is suppressed. Therefore, batteries incorporating the active material of the present invention have reduced gas generation, and the decrease in output characteristics caused by the deposition of dissolved metal ions on the negative electrode is suppressed. 【0028】 From the viewpoint of further improving the output characteristics of a battery incorporating the active material of the present invention and further reducing gas generation, it is preferable that the active material of the present invention has an appropriate amount of coating. Specifically, the Al element content in the active material is preferably 0.020% by mass or more, more preferably 0.025% by mass or more, and even more preferably 0.035% by mass or more. From a similar viewpoint, the Al element content in the active material is preferably 0.100% by mass or less, more preferably 0.080% by mass or less, and even more preferably 0.060% by mass or less. In order to uniformly form a coating containing such a trace amount of Al element, it is advantageous to employ, for example, the atomic deposition method described later. The Al element content in the active material is measured by ICP emission spectrometry. 【0029】The average thickness of the coating portion is preferably 15.0 nm or less, as this minimizes interference with the core's function as an active material and allows the core to fully perform as an active material. To further enhance this advantage, the average thickness of the coating portion is more preferably 8.0 nm or less, and even more preferably 3.0 nm or less. Furthermore, the average thickness of the coating portion is preferably 0.2 nm or more, from the viewpoint of further improving the output characteristics of the battery incorporating the active material of the present invention and further reducing gas generation. To further enhance this advantage, the average thickness of the coating portion is more preferably 0.3 nm or more, and even more preferably 0.5 nm or more. To uniformly form such a thin coating portion, it is advantageous to employ, for example, the atomic deposition method described later. 【0030】 The average thickness is the average value of the coating thickness on individual active material particles. The average thickness can be measured, for example, by a scanning transmission electron microscope (STEM). It can also be analyzed and measured using energy-dispersive X-ray spectroscopy (EDS) as needed. Specifically, line analysis can be performed on the surface of the active material, and the peak width of element A can be measured as the coating thickness from the results. The average thickness can be the average value obtained when the surface of the active material is measured at 10 locations using the above method. 【0031】 [Active Material] The shape of the active material of the present invention is not particularly limited, but particulate matter is one example. The particle size of the active material of the present invention is the cumulative volume particle size D at 50% of the cumulative volume, as measured by laser diffraction scattering particle size distribution analysis. ５０ (Hereinafter also referred to as "average particle diameter") is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 4 μm or more. This is because excessive aggregation of particles is suppressed, resulting in good dispersibility. On the other hand, the volume cumulative particle size D ５０ The particle size is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. This is because it ensures sufficient contact between the active material particles and between the active material particles and the solid electrolyte particles. 【0032】 Here, volume cumulative particle size D ５０ This has meaning as a substitute value for the average diameter of particles, including primary and secondary particles. "Primary particle" refers to the smallest unit particle surrounded by a grain boundary when observed with an SEM (scanning electron microscope, e.g., 500 to 5000x magnification). On the other hand, in this invention, "secondary particle" refers to a particle that is independent of other particles, formed by the aggregation of multiple primary particles sharing a portion of their outer circumference (grain boundary). 【0033】 Volume cumulative particle size D ５０ For example, the volume cumulative particle size D is measured using the following method: An automatic sample feeder for laser diffraction particle size distribution analyzers (Microtrac SDC, manufactured by Microtrac-Bell Corporation) is used to immerse the active material powder in a solvent mixture of 20% by mass ethanol and 0.1% by mass hexametaphosphoric acid. After irradiating with 40W ultrasound at a flow rate of 40% for 90 seconds, the particle size distribution is measured using the Microtrac-Bell Corporation laser diffraction particle size distribution analyzer "MT3000II". The volume cumulative particle size D is then measured from the obtained volume-based particle size distribution chart. ５０ Measure D ５０ When measuring, the water-soluble solvent was passed through a 60 μm filter, the "solvent refractive index" was set to 1.33, the particle permeability condition to "permeation", the measurement range to 0.243 μm to 704.0 μm, the measurement time to 30 seconds, and the average of two measurements was taken as D ５０ Let's assume that. 【0034】 The active material of the present invention is characterized by the intensity ratio of two specific peaks observed in its X-ray diffraction pattern. Specifically, the peak intensity of the peak observed at 2θ = 44.2 ± 0.5° (hereinafter also referred to as "peak A") in the X-ray diffraction pattern of the active material of the present invention, as measured by an X-ray diffractometer, is defined as I Ａ The peak intensity of the peak observed at 2θ = 18.7 ± 0.5° (hereinafter also referred to as "peak B") is set to I Ｂ In that case, I Ｂ I Ａ Value I Ａ / I ＢIt is preferable that the ratio is 0.46 or less. Peak A is a peak originating from a crystal plane containing metal atoms (e.g., Mn atoms) in the spinel-type composite oxide, and is a peak originating from an energetically stable plane. Peak B is a peak originating from a crystal plane containing oxygen atoms in the spinel-type composite oxide. Therefore, I Ａ / I Ｂ A value of 0.46 or less means that the number of metal atoms located on the outermost surface of the spinel-type composite oxide crystal is sufficiently small, and as a result, the elution of metal ions (e.g., Mn ions) from the active material into the electrolyte is suppressed. Ａ / I Ｂ A value of 0.46 or less means that there are many oxygen atoms on the core surface, and the coating evenly covers the core, resulting in minimal exposure of the core surface. From the perspective of making this advantage more pronounced, Ａ / I Ｂ It is more preferable that the value is 0.45 or less, and even more preferable that it is 0.44 or less. 【0035】 Furthermore, from the viewpoint of reducing the amount of gas generated in a battery incorporating the active material of the present invention, and from the viewpoint of making the crystals of the active material less reactive with the electrolyte and reducing the amount of gas generated in the battery, the above ratio I Ａ / I Ｂ It is preferably 0.30 or higher, more preferably 0.33 or higher, and even more preferably 0.36 or higher. 【0036】 If multiple peaks are observed within the range of 2θ = 44.2 ± 0.5°, the peak with the highest intensity observed within this range is designated as Peak A. Similarly, if multiple peaks are observed within the range of 2θ = 18.7 ± 0.5°, the peak with the highest intensity observed within this range is designated as Peak B. 【0037】 I Ａ / I Ｂ To set this within the range described above, for example, in the manufacturing method described later, the firing temperature and firing time of the mixed powder in the first firing step can be appropriately selected. 【0038】The X-ray diffraction pattern of the active material is measured using CuKα1 radiation. Other measurement conditions will be described in the examples below. 【0039】 From the viewpoint of improving the output characteristics of a battery incorporating the active material of the present invention, the BET specific surface area (hereinafter also simply referred to as "specific surface area") of the active material of the present invention is 0.5 m². ２ It is preferable that it be 0.6 m or more. ２ It is more preferable that it be 0.7 m or more per g, ２ It is even more preferable that the amount is greater than or equal to / g. Furthermore, from the viewpoint of reducing the amount of gas generated in a battery incorporating the active material of the present invention, the specific surface area of ​​the active material of the present invention is 2.0 m². ２ It is preferable that the amount be less than or equal to 1.8 m ２ It is more preferable that it be less than or equal to 1.6 m ２ It is even more preferable that the specific surface area be less than or equal to / g. In order to set the specific surface area within the above numerical range, for example, in the first firing step of the manufacturing method described later, the firing temperature should be set to 850°C or higher and the firing time to 30 hours or higher. The BET specific surface area can be measured using a nitrogen-helium mixed gas containing 30% by volume of nitrogen as the adsorbent gas and 70% by volume of helium as the carrier gas, and a specific surface area measuring device (for example, Macsorb 1230 manufactured by Mountec), in accordance with "(3.5) Single-point method" of "6.2 Flow method" in JIS R 1626 "Method for measuring the specific surface area of ​​fine ceramic powder by gas adsorption BET method". 【0040】 [Method for Manufacturing the Active Material] Next, a preferred method for manufacturing the active material of the present invention will be described. This manufacturing method is broadly divided into two steps: forming a core portion containing a spinel-type composite oxide containing Li, Ni, Mn, and Ti elements, and forming a coating portion containing Al oxide on the surface of the core portion by atomic deposition (hereinafter also referred to as "ALD"). These steps will be described in order below. 【0041】1. Formation of the core The core can be manufactured, for example, by carrying out the following steps (A) to (E) in this order. However, the method of manufacturing the core is not limited to this method, and for example, the firing step may be performed once or twice. (A) A step of mixing raw materials to obtain a mixed powder (mixing step). (B) A step of firing the mixed powder to obtain a first fired product (first firing step). (C) A step of firing the first fired product to obtain a second fired product (second firing step). (D) A step of crushing the second fired product to obtain a crushed product with adjusted particle size (crushing step). (E) A step of firing the crushed product to obtain the core (third firing step). 【0042】 The first firing process is a firing process to crystallize the active material to a certain size. The second firing process is a firing process to improve crystallinity without increasing particle size. The third firing process is a firing process to sufficiently incorporate oxygen into the active material. By performing the firing process in this way, according to its purpose, an active material that can reduce the amount of gas generated by the battery can be obtained. The details of each process are explained below. 【0043】 (A) Mixing Process In this process, raw materials containing Li, Ni, Mn, and Ti are mixed to obtain a mixed powder. Oxides, hydroxides, carbonates, etc. of each metal element can be used as raw materials, and specifically, for example, lithium carbonate powder, manganese dioxide powder, nickel hydroxide powder, and titanium(IV) oxide powder can be used. The mixing ratio of the raw materials should be adjusted as appropriate according to the elemental composition of the target core. A dispersant may also be added to the mixed powder. For example, ammonium polycarboxylate can be used as a dispersant. The dispersant content is preferably 3% by mass or more and 10% by mass or less of the total mass of the mixed powder. The mixing of each of the above raw materials is preferably carried out wet. 【0044】 After mixing the raw materials to obtain a mixture, the mixture is then pulverized. Pulverization can be carried out, for example, by wet pulverization using a wet pulverizer. Next, the pulverized powder obtained in this way is granulated and dried. The active material to be manufactured is I Ａ / I ＢFrom the viewpoint of making it easier to set the value within the above-mentioned numerical range, it is preferable to use the spray drying method for granulation and drying of the crushed powder. 【0045】 (B) Once the mixed powder is obtained in the first firing step, the mixed powder is then fired. The firing temperature in the first firing step is preferably 700°C or more and 1050°C or less, more preferably 750°C or more and 1000°C or less, and even more preferably 800°C or more and 950°C or less. By carrying out the first firing step at such firing temperatures, the active material is crystallized to a certain size, and the I of the active material to be produced is Ａ / I Ｂ The value can be set within the above-mentioned numerical range. From a similar viewpoint, the firing time in the first firing step is preferably 10 hours or more and 60 hours, more preferably 20 hours or more and 50 hours, and even more preferably 30 hours or more and 45 hours. In the heating process until the target firing temperature is reached, the temperature may be continuously increased over time. Alternatively, a period in which the temperature becomes constant may be provided during the heating process (the same applies to the second and third firing steps described below). The firing atmosphere in the first firing step can be either an oxidizing atmosphere such as an oxygen-containing atmosphere or an inert atmosphere such as a nitrogen atmosphere. The first fired product obtained by firing under the above conditions is used in the next step after being cooled to room temperature. If necessary, the first fired product that has been cooled to room temperature may be crushed or classified before being used in the next step. 【0046】(C) Second firing process In this process, the first fired product is fired to obtain the second fired product. The firing temperature in the second firing process is preferably 580°C to 950°C, more preferably 600°C to 900°C, and even more preferably 650°C to 850°C. By carrying out the second firing process at these temperatures, the crystallinity can be improved without increasing the particle size. From a similar viewpoint, the firing time in the second firing process is preferably 10 hours to 60 hours, more preferably 20 hours to 50 hours, and even more preferably 30 hours to 45 hours. The firing atmosphere in the second firing process can be either an oxidizing atmosphere such as an oxygen-containing atmosphere or an inert atmosphere such as a nitrogen atmosphere. The second fired product obtained by firing under the above conditions is used in the next process after being cooled to room temperature. If necessary, the second fired product that has been cooled to room temperature may be crushed or classified before being used in the next process. 【0047】 From the viewpoint of improving crystallinity without increasing particle size, the firing temperature of the second firing step is preferably 80°C or more lower than the firing temperature of the first firing step, more preferably 120°C or more lower, and even more preferably 150°C or more lower. 【0048】 (D) Grinding process Once the second calcined product is obtained, the second calcined product is ground to obtain a pulverized product with adjusted particle size. Grinding can be performed using, for example, a jet mill, a counterjet mill, or an orient mill. Grinding is performed to determine the average particle size of the pulverized product (volume cumulative particle size at 50% cumulative volume measured by laser diffraction scattering particle size distribution method D ５０It is preferable that the particle size of the pulverized material be between 1 μm and 50 μm, more preferably between 3 μm and 30 μm, and even more preferably between 5 μm and 20 μm. Prior to pulverizing the second calcined material, the second calcined material may be washed with water to remove impurities. If washing is performed, it is preferable to dry the second calcined material after washing before pulverizing it. Drying of the second calcined material after washing may be done once or two or more times. If drying is performed twice, the temperature for the first drying is preferably between 60°C and 300°C, more preferably between 80°C and 200°C, and the drying time is preferably between 1 hour and 30 hours, more preferably between 6 hours and 20 hours. Drying can also be performed under the same conditions if it is done only once. Furthermore, if drying is performed twice, the temperature for the second drying is, for example, 300°C to 700°C, more preferably 400°C to 600°C, and the drying time is preferably 3 hours to 14 hours, more preferably 5 hours to 10 hours. Regardless of how many times drying is performed, drying may be carried out under atmospheric pressure or under reduced pressure. 【0049】 (E) Third firing process In this process, the pulverized material obtained in the crushing process is fired to obtain the core. The firing temperature in the third firing process is preferably 550°C to 900°C, more preferably 600°C to 850°C, and even more preferably 650°C to 800°C. By carrying out the third firing process at these temperatures, sufficient oxygen can be incorporated into the active material. From a similar viewpoint, the firing time in the third firing process is preferably 1 hour to 35 hours, more preferably 5 hours to 30 hours, and even more preferably 10 hours to 25 hours. 【0050】 The third calcination step is preferably carried out under an oxidizing gas atmosphere such as an oxygen-containing atmosphere, and more preferably under an oxygen gas atmosphere. After the calcination described above, the powder properties such as the particle size of the core may be adjusted by crushing and / or classification. 【0051】From the viewpoint of ensuring that the active material contains a sufficient amount of oxygen, the firing temperature of the third firing step is preferably 30°C or more lower than the firing temperature of the second firing step, more preferably 50°C or more lower, and even more preferably 60°C or more lower. 【0052】 2. Formation of the coating Once the core is obtained, a coating containing Al oxide is formed on the surface of the core using ALD. Since ALD theoretically allows for the formation of the coating layer one atomic layer at a time, a thin and dense coating can be formed. Another method for forming the coating is the sol-gel method, for example, but it is not easy to form a thin and dense coating using the sol-gel method. Furthermore, forming the coating with ALD tends to result in a smaller specific surface area of ​​the active material compared to other methods, and this makes it easier to control the specific surface area within the above range, which is also an advantage. 【0053】 Specifically, the coating can be manufactured by performing the following steps (F) to (J) in this order: (F) A step of introducing the core into the reaction chamber. (G) A step of heating the reaction chamber to remove moisture adhering to the core. (H) A step of adding the precursor material of the coating into the reaction chamber. (I) A step of removing the precursor material from the reaction chamber and then adding the reactant to the chamber. (J) A step of removing excess reactant and reaction products from the gas phase. (K) A step of repeating steps (H) to (J). 【0054】 In step (F), it is preferable to introduce an inert gas into the reaction chamber to form a fluidized bed. For example, nitrogen or argon can be used as the inert gas. 【0055】 The heating temperature in process (G) can be set, for example, within the range of 100°C to 200°C. The heating time can also be set, for example, within the range of 1 hour to 12 hours. 【0056】In step (H), the reaction chamber is heated to the film formation temperature, and then the precursor material is added to the reaction chamber. The heating temperature in this step is not particularly limited as long as it is a temperature at which a coating can be formed, but can be set in the range of 50°C to 400°C, for example. Examples of precursor materials include organoaluminum compounds, such as trimethylaluminum (hereinafter also referred to as "TMA"). In step (H), the heated precursor material may also be added to the reaction chamber. The heating temperature for the precursor material can be set, for example, to room temperature or higher and 300°C or lower. It is preferable that step (H) is carried out until the precursor material is chemically adsorbed onto the surface of the core to form a single phase. The removal of the precursor material in step (I) can be carried out by purging the reaction chamber with an inert gas such as nitrogen, for example. Examples of reactants used in step (I) include H ２ O, O ３ H ２ O ２ H ２ Plasma, O ２ Plasma, Ar plasma, N ２ Examples include O-plasma. 【0057】 In step (J), excess precursor reagents and reaction products can be removed, for example, by purging. Examples of reaction products include methane gas. 【0058】 In step (K), the operations in steps (H) to (J) are repeated until the desired film thickness is obtained, thereby successfully forming a thin and dense coating. Alternatively, the operations in steps (H) to (J) may be repeated until the Al element content in the active material falls within the desired numerical range. 【0059】 In addition to TMA, AlMe is used as a precursor for forming the coating. ２ O ｉ Pr, AlMe ２ H, AlMe ２ Cl, AlMe ２ (C ３ H ６ NMe ２ ), AlH ３N: (C ５ H １１ ), AlEt ３ 、AlCl ３ 、AlBu ３ 、Al ２ (NMe ２ ) ６ 、Al(O ｓ Bu) ３ 、Al(O ｎ Pr) ３ 、Al(OEt) ３ 、Al(NMe ２ ) ３ 、Al(N ｉ Pr ２ ) ３ 、Al(N ｉ Pr ２ ) ２ (C ３ H ６ NMe ２ )、Al(NEt ２ ) ３ 、Al(NEt ２ ) ２ (C ３ H ６ NMe ２ )、Al(mmp) ３ 、Al( ｉ PrAMD)Et ２ 、Al(CH ３ ) ３ etc. are mentioned. When forming the coating by ALD, in addition to the organoaluminum compound as the precursor substance, an organometallic compound other than aluminum may be used in combination. In this case, a coating containing aluminum oxide and metal oxide other than aluminum can be obtained. 【0060】[Electrode Mixture] The active material of the present invention obtained in this manner can be used, for example, in the form of an electrode mixture containing the active material and an electrolyte. The electrolyte may be a solid or a liquid. When a solid electrolyte is used as the electrolyte, the content of the active material in the electrode mixture may be 30% by mass or more, 40% by mass or more, or 50% by mass or more, when the total solid content is considered to be 100% by mass. Alternatively, the content of the active material may be, for example, 98% by mass or less, 90% by mass or less, or 85% by mass or less. By having the content of the active material within the above range, the electrode can fully exhibit its function. 【0061】 The electrolyte that can be used in the present invention can be the same as the electrolyte used in general liquid-type batteries, and may be a non-aqueous electrolyte or an aqueous electrolyte. For example, organic electrolytes, polymer solid electrolytes, molten salts, etc. can be used. Examples of organic electrolytes include esters such as propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, etc. as solvents, substituted tetrahydrofurans such as tetrahydrofuran and 2-methyltetrahydrofuran, ethers such as dioxolane, diethyl ether, dimethoxyethane, diethoxyethane, methoxyethoxyethane, etc., dimethyl sulfoxide, sulfolane, methylsulfolane, acetonitrile, methyl formate, methyl acetate, etc., and one or more of these as mixed solvents can be used. In addition, examples of electrolyte salts that dissolve in organic solvents include lithium perchlorate, lithium borofluoride, lithium hexafluoride phosphate (hereinafter referred to as "LiPF") ６ Examples include lithium salts such as lithium hexafluoride, lithium trifluoromethanesulfonate, lithium halides, and lithium aluminate chloride. 【0062】The solid electrolyte that can be used in the present invention can be the same as the solid electrolyte used in general solid batteries, as long as it has lithium ion conductivity. Examples include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes, but sulfide solid electrolytes are preferred. The sulfide solid electrolyte may contain lithium (Li) and sulfur (S) and have lithium ion conductivity, or it may contain lithium (Li), phosphorus (P), and sulfur (S) and have lithium ion conductivity. The sulfide solid electrolyte may be a crystalline material, glass ceramic, or glass. The sulfide solid electrolyte may have a crystalline phase with an argyrodite structure. Examples of such sulfide solid electrolytes include Li ２ S-P ２ S ５ Li ２ S-P ２ S ５ -LiX (where X is at least one halogen element), Li ２ S-P ２ S ５ -P ２ O ５ Li ２ S-Li ３ PO ４ -P ２ S ５ Li ３ PS ４ Li ４ P ２ S ６ Li １０ GeP ２ S １２ Li ３．２５ Ge ０．２５ P ０．７５ S ４ Li ７ P ３ S １１ Li ３．２５ P ０．９５ S ４ Li ａ PS ｂ X ｃExamples include compounds represented by (X is at least one halogen element; a represents a number between 3.0 and 6.0; b represents a number between 3.5 and 4.8; c represents a number between 0.1 and 3.0). In addition, examples include sulfide solid electrolytes described in International Publication WO2013 / 099834A1 and International Publication WO2015 / 001818A1. 【0063】 The active material contained in the electrode mixture may consist solely of the active material of the present invention, or it may be a combination of the active material of the present invention and other active materials. Examples of other active materials include particles made of known lithium transition metal composite oxides. When using the active material of the present invention in combination with other active materials, it is preferable that the active material of the present invention is contained in an amount of 50% by mass or more, and particularly 70% by mass or more, relative to the total amount of active materials. 【0064】 [Battery] The active material of the present invention can be suitably used as a positive electrode active material for a battery. The battery may be a primary battery or a secondary battery. The battery of the present invention may, for example, have a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer and containing an electrolyte. The positive electrode layer contains the active material of the present invention. The active material of the present invention is particularly suitably used as a positive electrode active material for a non-aqueous electrolyte secondary battery in which the electrolyte is liquid. 【0065】 Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to such embodiments. For example, in the above-described manufacturing method, the coating layer was formed by ALD, but the method of forming the coating layer is not limited to this. Examples of methods for forming the coating layer other than ALD include chemical vapor deposition (CVD), pulsed laser deposition (PLD), sputtering, vacuum deposition, electron beam deposition, and molecular beam epitaxy (MBE). However, from the viewpoint of further reducing the amount of gas generated in a battery incorporating the active material of the present invention, it is preferable to use ALD as the method for forming the coating layer. 【0066】The above embodiments of the present invention encompass the following technical concepts: [1] An active material having a core portion and a coating portion located on the surface of the core portion, wherein the core portion comprises a spinel-type composite oxide containing lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti), the molar ratio Ti / (Li+Ni+Mn+Ti) of the titanium (Ti) element content to the total content of lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements in the core portion is 0.030 or more and 0.100 or less, the coating portion comprises an aluminum (Al) oxide, the aluminum (Al) element content in the active material is 0.020% by mass or more and 0.100% by mass or less, and the specific surface area of ​​the active material is 0.5 m² ２ / g or more 2.0m ２ The value is less than or equal to / g, and the peak intensity of the peak observed at 2θ = 44.2 ± 0.5° in the X-ray diffraction pattern of the active material measured by an X-ray diffractometer using CuKα1 rays is I Ａ The peak intensity of the peak observed at 2θ = 18.7 ± 0.5° in the aforementioned X-ray diffraction pattern is defined as I Ｂ In that case, I Ｂ I Ａ Value I Ａ / I ＢAn active material in which the ratio is between 0.30 and 0.46. [2] The active material according to [1], wherein the molar ratio Li / (Li+Ni+Mn+Ti) of the content of lithium (Li) element to the total content of lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements in the core portion is 0.300 or more and 0.400 or less, the molar ratio Ni / (Li+Ni+Mn+Ti) of the content of nickel (Ni) element to the total content of lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements in the core portion is 0.100 or more and 0.200 or less, and the molar ratio Mn / (Li+Ni+Mn+Ti) of the content of manganese (Mn) element to the total content of lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements in the core portion is 0.400 or more and 0.500 or less. [3] A positive electrode active material for a non-aqueous electrolyte secondary battery as described in [1] or [2]. [4] An electrode mixture comprising the active material and electrolyte as described in any one of [1] to [3]. [5] A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer and containing an electrolyte, wherein the positive electrode layer contains the active material as described in any one of [1] to [3]. [6] A method for producing the active material as described in any one of [1] to [3], comprising forming a coating portion containing aluminum (Al) oxide on the surface of the core portion containing a spinel-type composite oxide containing lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements by atomic deposition. [7] The active material as described in any one of [1] to [3], wherein the coating portion is formed by atomic deposition. 【0067】 The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass%". 【0068】[Example 1] (1) Preparation of the core Lithium carbonate, manganese dioxide, nickel(II) hydroxide, titanium(IV) oxide, and ammonium polycarboxylate (dispersant, SN Dispersant 5468 manufactured by Sunopco) were mixed in water and then pulverized in a wet mill. After that, the mixture was granulated and dried using a hot spray dryer to obtain a mixed powder. The mixing ratio of each metal compound contained in the mixed powder was adjusted so that the content ratio of Li, Mn, Ni, and Ti elements in the obtained core was as shown in Table 1. The mixing ratio of the dispersant was 6% by mass of the total amount of the raw materials. Next, the obtained mixed powder was calcined at 885°C for 37 hours in an air atmosphere, the calcined product was cooled to room temperature, and the calcined product was further pulverized in an Orient Mill (Orient Vertical Cutting Mill, Model: VM-22, manufactured by Orient Crushing Machinery Co., Ltd.) to obtain the first calcined product. The first calcined product was calcined at 740°C for 37 hours in an air atmosphere, and then cooled to room temperature. Next, the calcined product was pulverized using the Orient Mill, then classified using a sieve with a mesh size of 53 μm, and the sieved material was collected to obtain the second calcined product. The second calcined product was washed with water and then dried at 120°C for 12 hours, followed by drying at 500°C for 7 hours. The resulting dried product was pulverized using a counterjet mill (Hosokawa Micron Corporation, model: 100AFG) to obtain an average particle size D ５０ A pulverized material with a particle size of 3.00 μm was obtained. This pulverized material was calcined at 724°C for 15 hours under an oxygen gas stream. After calcination, the material was classified using a sieve with a mesh size of 53 μm, and the material below the sieve was collected to obtain the core. 【0069】(2) Formation of the coating The coating was formed by ALD comprising the following steps (F) to (K). <Step (F)> 50 g of the core was introduced into the reaction chamber and the chamber was purged with nitrogen. <Step (G)> It was heated at 120°C for 16 hours to remove moisture adhering to the core. <Step (H)> After raising the temperature inside the chamber to 120°C, TMA was introduced into the reaction chamber and it was confirmed that TMA was saturated adsorbed onto the core. <Step (I)> After purging the reaction chamber with nitrogen to remove excess TMA, water vapor was introduced into the reaction chamber to completely react the TMA with water. <Step (J)> The reaction chamber was purged with nitrogen to remove excess water vapor and reaction products such as methane. <Step (K)> By repeating steps (H) to (J) above, a coating was formed on the surface of the core and an active material was obtained. Steps (H) to (J) were performed for a total of two cycles. 【0070】 [Example 2] An active material was obtained in the same manner as in Example 1, except that steps (H) to (J) were performed for three cycles. 【0071】 [Example 3] Active material was obtained in the same manner as in Example 1, except that after the third firing process, the material was crushed using a pin mill type pulverizer (Exceed Mill manufactured by Makino Sangyo Co., Ltd., 4000 rpm), and then the material was further classified using a sieve with a mesh size of 53 μm and the material below the sieve was collected to obtain the core, and that steps (H) to (J) were repeated for three cycles. 【0072】 [Example 4] Active material was obtained in the same manner as in Example 1, except that the core was obtained by coprecipitation and steps (H) to (J) were performed for three cycles. 【0073】 [Comparative Example 1] An active material was obtained in the same manner as in Example 1, except that no coating was formed. Therefore, the active material of Comparative Example 1 corresponds to the core portion of Example 1. 【0074】 [Comparative Example 2] An active material was obtained in the same manner as in Example 1, except that one cycle of steps (H) to (J) was performed (step K was not performed). 【0075】[Comparative Example 3] An active material was obtained in the same manner as in Example 1, except that steps (H) to (J) were performed for 10 cycles. 【0076】 [Comparative Example 4] An active material was obtained in the same manner as in Example 1, except that the proportion of each metal compound contained in the mixed powder was changed so that the content ratios of Li, Mn, Ni, and Ti elements in the resulting core portion were as shown in Table 1, and steps (H) to (J) were performed for three cycles. 【0077】 [Comparative Example 5] An active material was obtained in the same manner as in Example 1, except that the firing temperature in the first firing step of the mixed powder was set to 800°C and steps (H) to (J) were performed for three cycles. 【0078】 [Evaluation] The active materials obtained in the examples and comparative examples were evaluated as follows. 【0079】[Content of each element in the active material] The content of Li, Ni, Mn, Ti, and Al in the active materials obtained in the examples and comparative examples was measured by ICP emission spectrometry. Specifically, the active material to be analyzed was dissolved in hydrochloric acid to obtain measurement sample 1. Separately, the active material to be analyzed was mixed with sodium peroxide and sodium carbonate, and then heated with a portable gas burner to obtain a molten salt. This was then added to hydrochloric acid and dissolved to obtain measurement sample 2. Measurement sample 1 was used for the quantification of Li, Ni, and Mn elements, and measurement sample 2 was used for the quantification of Ti and Al elements. The content of each metal element in these measurement samples was measured using an ICP emission spectrometer (Hitachi High-Tech Corporation, model number: PS3520UVDDII). Based on these results, the molar ratios of Li, Ni, Mn, and Ti elements contained in the active material, Li / (Li+Ni+Mn+Ti), Ni / (Li+Ni+Mn+Ti), Mn / (Li+Ni+Mn+Ti), and Ti / (Li+Ni+Mn+Ti), were calculated. These results are shown in Table 1. Note that the coating does not contain Li, Ni, Mn, and Ti elements, or if it does, it is only in trace amounts, so the molar ratios of Li, Ni, Mn, and Ti elements contained in the active material (Li / (Li+Ni+Mn+Ti), etc.) can be considered to be the same as the molar ratios of Li, Ni, Mn, and Ti elements contained in the core. In Comparative Example 1, the ALD coating was not formed, but trace amounts of Al were detected. This Al element is considered to be an unavoidable impurity. 【0080】 [Average particle size D ５０ [and BET specific surface area] Average particle size D of the active material obtained in the examples and comparative examples ５０ The BET specific surface area was measured by the method described above. The results are shown in Table 1. 【0081】 [I Ａ / I Ｂ XRD measurements were performed on the active materials obtained in the examples and comparative examples, and the intensities of peak A and peak B described above were measured. Ａ and I Ｂ To find I Ａ / I ＢThe following was calculated. The XRD measurement conditions were as follows: • Fully automated multi-purpose X-ray diffractometer D8-ADVANCE (Bruker) • Radiation source: CuKα • Tube voltage: 40kV • Tube current: 40mA • Measurement method: Focused method (reflection method) • Detector: LYNXEYE-XE-T (energy dispersive detector) • Incident solar slit: 2.5° • Receiver solar slit: 2.5° • Measurement range: 2θ = 5 to 119.9372° • Scan speed: 0.09 sec / step 【0082】 [Preparation of Type 2032 Coin Cell] 89% by mass of the active material obtained in the Examples and Comparative Examples was mixed with 5% by mass of acetylene black as a conductive additive and 6% by mass of PVDF (polyvinylidene fluoride) as a binder. NMP (N-methylpyrrolidone) was added to this mixture to prepare a paste. This paste was uniformly applied to an Al foil current collector with a thickness of 15 μm and dried at 200°C. Then, it was pressed to a thickness of 65 μm to obtain a positive electrode sheet. This positive electrode sheet was cut to a diameter of 13 mm to obtain a positive electrode. Similarly, 89% by mass of lithium titanate (LTO) was mixed with 5% by mass of acetylene black as a conductive additive and 6% by mass of PVDF as a binder. NMP (N-methylpyrrolidone) was added to this mixture to prepare a paste. This paste was uniformly applied to an Al foil current collector with a thickness of 15 μm and dried at 200°C. Then, it was pressed to a thickness of 75 μm to obtain a negative electrode sheet. This negative electrode sheet was cut to a diameter of 14 mm to obtain the negative electrode. As the electrolyte, LiPF was used as the solute in a carbonate-based mixed solvent. ６ A solution of 1 mol / L of [the substance] was used. A 2032 type coin cell was fabricated using the above positive electrode, negative electrode, electrolyte, and separator (polypropylene). 【0083】[Capacity Retention Rate] The capacity retention rate was measured using the aforementioned 2032 type coin cell battery. First, the 2032 type coin cell battery was charged at 25°C with a constant current of 0.1C to 4.999V, and then charged at a constant voltage (4.999V) until the current value was 0.02C. After that, it was discharged at 0.1C to 3.000V. This was repeated for 3 cycles. The capacity at the time of discharge in the 3rd cycle was taken as the initial capacity. Next, the 2032 type coin cell battery was charged at 25°C with a constant current of 0.1C to 4.999V, and then charged at a constant voltage (4.999V) until the current value was 0.02C. After that, a cycle of constant current discharge to 3V was performed 7 times. The discharge rates during constant current discharge were 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, and 5C, respectively, from the 1st to the 7th cycle. The capacity retention rate, defined as the percentage of the initial capacity at discharge at 5C, is shown in Table 1. 【0084】 [Fabrication of Laminated Battery] The positive electrode sheet was cut to a size of 2.9 cm x 4.0 cm to obtain the positive electrode. The negative electrode sheet was cut to a size of 3.1 cm x 4.2 cm to obtain the negative electrode. The same electrolyte used in [Fabrication of Type 2032 Coin Battery] was used. The positive electrode, negative electrode, electrolyte, and separator (cellulose-based) were sealed in an outer container made of aluminum laminate film to produce a laminated battery. 【0085】[Gas Generation Evaluation Test] The laminated battery prepared by the method described above was left standing for 10 hours. This laminated battery was charged at 25°C with a constant current of 0.1C to 3.45V, and then charged at a constant voltage (4.999V) until the current value was 0.02C. After that, it was discharged at 0.1C to 1.5V with a constant current. This charge-discharge process was repeated three times. Next, the battery was left standing for 10 hours at an ambient temperature of 55°C, and then charged at 0.1C to 3.45V with a constant current, maintaining the potential difference between the electrodes for 168 hours from the start of charging. After that, it was discharged at 0.1C to 1.5V. The total amount of gas generated during these four charge-discharge cycles was measured by the immersion volume method (solvent displacement method based on Archimedes' principle). The above experiment was performed on three laminated batteries, and the arithmetic mean G of the measured gas generation amounts was calculated for each example and comparative example. Furthermore, using the arithmetic mean G0 of the gas generation amount in Comparative Example 1 as a reference, the reduction rate of gas generation amount in each example and comparative example was calculated based on the following formula (1). The results are shown in Table 1. Gas generation amount reduction rate (%) = 100 × (G0 - G) / G0 ... (1) 【0086】 【0087】 As is clear from Table 1, the batteries manufactured using the active materials of Examples 1 to 4 showed a good balance of superiority in both capacity retention rate during high-rate discharge and gas generation reduction rate compared to the batteries manufactured using the active materials of Comparative Examples 1 to 5. 【0088】 The present invention provides an active material that can be used to manufacture a battery with high output characteristics and low gas generation.

Claims

1. An active material having a core and a coating portion located on the surface of the core, wherein the core contains a spinel-type composite oxide containing lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti), the molar ratio Ti / (Li+Ni+Mn+Ti) of titanium (Ti) to the total content of lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) in the core is 0.030 or more and 0.100 or less, the coating portion contains an aluminum (Al) oxide, the aluminum (Al) content in the active material is 0.020% by mass or more and 0.100% by mass or less, and the specific surface area of ​​the active material is 0.5 m². ２ / g or more 2.0m ２ The value is less than or equal to / g, and the peak intensity of the peak observed at 2θ = 44.2 ± 0.5° in the X-ray diffraction pattern of the active material measured by an X-ray diffractometer using CuKα1 rays is I Ａ The peak intensity of the peak observed at 2θ = 18.7 ± 0.5° in the aforementioned X-ray diffraction pattern is defined as I Ｂ In that case, I Ｂ I Ａ Value I Ａ / I Ｂ An active material in which the ratio is between 0.30 and 0.

46.

2. The active material according to claim 1, wherein the molar ratio Li / (Li+Ni+Mn+Ti) of the content of lithium (Li) element to the total content of lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements in the core portion is 0.300 or more and 0.400 or less, the molar ratio Ni / (Li+Ni+Mn+Ti) of the content of nickel (Ni) element to the total content of lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements in the core portion is 0.100 or more and 0.200 or less, and the molar ratio Mn / (Li+Ni+Mn+Ti) of the content of manganese (Mn) element to the total content of lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements in the core portion is 0.400 or more and 0.500 or less.

3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2.

4. An electrode mixture comprising the active material and electrolyte according to claim 1 or 2.

5. A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer and containing an electrolyte, wherein the positive electrode layer contains the active material described in claim 1 or 2.

6. A method for producing an active material according to claim 1 or 2, comprising forming a coating portion containing aluminum (Al) oxide on the surface of the core portion containing a spinel-type composite oxide containing lithium (Li), nickel (Ni), manganese (Mn), and titanium (Ti) elements by atomic deposition.

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