Coated active material and method for producing a coated active material

Abstract

To provide a coated active material that can suppress an increase in battery resistance.SOLUTION: A coated active material includes an electrode active material and a coating layer that coats the electrode active material, and the coating layer contains an oxide solid electrolyte that includes Li, P, and O elements, and the particle diameter (D50) of the coated active material is 5.5 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a coated active material and a method for producing a coated active material. [Background technology]

[0002] In recent years, battery development has been booming. For example, in the automotive industry, development is progressing on batteries used in electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), and hybrid electric vehicles (HEVs). It is also known that the surface of the electrode active material used in batteries is coated with a coating layer.

[0003] For example, Patent Document 1 discloses composite particles comprising positive electrode active material particles and a coating film containing a phosphorus compound that covers at least a portion of the surface of the positive electrode active material particles. Furthermore, Patent Document 1 discloses the production of composite particles by mixing positive electrode active material particles with an aqueous coating liquid (aqueous coating solution) containing phosphorus and drying the mixture. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-136763 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] From the viewpoint of the chemical stability and ionic conductivity of the coating film (coating layer), the use of phosphorus (P) in the coating layer is being considered. On the other hand, compounds used as phosphorus sources, such as phosphoric acid, have high viscosity, which can cause aggregation when forming the coating layer, potentially increasing the particle size of the coating active material. If the particle size of the coating active material increases, the battery resistance may increase.

[0006] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a coated active material capable of suppressing an increase in battery resistance. **Means for Solving the Problems**

[0007] [1] A coated active material having an electrode active material and a coating layer that coats the electrode active material, wherein the coating layer contains an oxide solid electrolyte containing Li element, P element and O element, and the particle diameter (D 50 ) of the coated active material is not more than 5.5 μm.

[0008] [2] The coated active material according to [1], wherein the particle diameter (D 50 ) is not less than 1.0 μm.

[0009] [3] The coated active material according to [1] or [2], wherein the oxide solid electrolyte further contains B element or La element.

[0010] [4] A method for producing a coated active material, which produces the coated active material according to any one of [1] to [3], the method comprising: a slurry preparation step of preparing a slurry containing the electrode active material, the oxide solid electrolyte, and a solvent for dissolving the oxide solid electrolyte; a coating layer formation step of forming the coating layer by a spray drying method in which the slurry is sprayed and dried together with atomizing air. The method for producing a coated active material, wherein the gas-liquid ratio in the spray drying method is 5.0×10 -3 or less.

[0011] [5] The method for producing a coated active material according to [4], wherein the flow rate of the atomizing air is 60 L / min or more. **Advantages of the Invention**

[0012] This disclosure provides a coating active material that can suppress the increase in battery resistance. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view illustrating an example of a coated active material in this disclosure. [Figure 2] This is a schematic cross-sectional view illustrating a battery in this disclosure. [Figure 3] This is a flowchart illustrating the method for producing the coated active material in this disclosure. [Figure 4] This graph shows the relationship between the gas-liquid ratio and particle size in the examples and comparative examples. [Figure 5] This is an SEM image of the coated active material prepared in Example 1. [Modes for carrying out the invention]

[0014] The coated active material and the method for producing the coated active material described herein will be explained in detail below.

[0015] A. Coated active material The coating active material in this disclosure comprises an electrode active material and a coating layer that coats the electrode active material. The coating layer also contains an oxide solid electrolyte containing Li, P, and O elements. In particular, the coating active material in this disclosure has a particle size (D 50 The size is 5.5 μm or less.

[0016] The coated active material in this disclosure has a particle size (D 50 Since the thickness is 5.5 μm or less, it can suppress the increase in battery resistance when used in a battery.

[0017] From the perspective of suppressing battery resistance, it is preferable that the particle size of the coated active material is small. This is because by increasing the specific surface area of the coated active material, the contact area with the electrolyte can be increased. Also, because the diffusion distance of carrier ions within the coated particles can be reduced. On the other hand, as described above, when the coating layer contains phosphorus (P), there is a risk that the active material will granulate and the particle size of the coated active material will increase, and there are issues in suppressing battery resistance by reducing the particle size of the coated active material. In this regard, as a result of intensive studies on the conditions for producing the coated active material using the so-called spray drying method, the present inventor found that by setting the gas-liquid ratio in the spray drying method to 5.0×10 -3 as follows, granulation can be suppressed and the particle size (D 50 ) of the coated active material can be reduced. Generally, when the gas-liquid ratio is reduced, the flow rate of the atomizing air relatively increases. When the flow rate of the atomizing air is large, it is considered that the coating liquid can coat the active material in a sufficiently misted state, so that a uniform and thin coating layer can be formed. When the thickness of the coating layer is large, aggregation and granulation of the coated particles are likely to occur due to the phosphorus contained in the coating layer, and it is considered that the particle size of the coated active material will increase. However, when the thickness of the coating layer is small, it is considered that such aggregation can be suppressed.

[0018] Also, in the manufacture of a battery, it is assumed that the electrode layer will be pressed. In this regard, if the particle size of the coated active material increases due to granulation, the coated active material is likely to deform due to the above pressing, and there is a risk that cracks will occur in the electrode layer along with the deformation of the coated active material, which may be a factor for increasing the battery resistance. On the other hand, since the coated active material in the present disclosure has a small particle size, that is, since aggregation is suppressed, it is also possible to suppress an increase in battery resistance caused by cracks in the electrode layer.

[0019] The coated active material in the present disclosure has a particle size (D 50 ) of 5.5 μm or less. D 50 may be 5.0 μm or less, may be 4.5 μm or less, or may be 4.0 μm or less. On the other hand, D 50For example, the particle size is 1.0 μm or larger, and may be 2.0 μm or larger, or 3.0 μm or larger. In addition, the coating active material has a particle size (D 10 The particle size (D) is not particularly limited, but for example, it is 0.5 μm or more and 3.0 μm or less. In addition, the coating active material has a particle size (D) 90 The particle size D is not particularly limited, but for example, it is between 3.0 μm and 15.0 μm. 10 , particle size D 50 and particle size D 90 These correspond to particle sizes corresponding to a cumulative 10% volume%, a cumulative 50% volume%, and a cumulative 90% volume%, respectively, as measured by a laser diffraction particle size distribution analyzer.

[0020] Furthermore, it is preferable that the particle size variation in the coating active material is small. The particle size variation is (particle diameter D 50 ) / (particle size D 90 - Particle size D 10 This can be determined by the following method. The particle size variation is, for example, 0.4 or more and 1.1 or less.

[0021] 1.Coating layer The coating layer is a layer that covers the electrode active material. The coating layer also contains an oxide solid electrolyte containing Li, P, and O elements.

[0022] The proportion of Li element in the oxide solid electrolyte is not particularly limited, but is, for example, between 20 mol% and 50 mol%. The proportion of P element in the oxide solid electrolyte is not particularly limited, but is, for example, between 5 mol% and 20 mol%. The proportion of each element can be calculated, for example, by ICP (inductively coupled plasma) analysis.

[0023] Furthermore, the proportion of element O can be determined as the oxygen concentration, for example, by the heating and melting method. The oxygen concentration of the oxide solid electrolyte in this disclosure, as determined by the heating and melting method, is, for example, 45% by weight or more and 60% by weight or less. The molar ratio of element O in the oxide solid electrolyte is not particularly limited, but is, for example, 30 mol% or more and 60 mol% or less.

[0024] Furthermore, the oxide solid electrolyte may further contain element B or element La. The molar ratio of element B to element P (B / P) is not particularly limited, but for example, it is between 0.5 and 2.0. The molar ratio of element Li to the sum of elements P and B (Li / (P+B)) is not particularly limited, but for example, it is between 0.3 and 1.2. The molar ratio of element La to element P (La / P) is, for example, between 0.005 and 0.15.

[0025] The coverage rate of the coating layer over the electrode active material is not particularly limited, but may be, for example, 75% or more, or 80% or more. If the coverage rate is too low, it may not be possible to sufficiently suppress the increase in resistance caused by the high-resistance layer resulting from the reaction between the electrode active material and the electrolyte. On the other hand, the coverage rate may be 100%, or less than 100%. In this disclosure, the coverage rate is determined by calculating the elemental ratio from the intensity ratio of each major element based on X-ray photoelectron spectroscopy (XPS) measurements, and is determined as the ratio of the elements contained in the coating layer to the total of the elements contained in the electrode active material and the elements contained in the coating layer.

[0026] The thickness of the coating layer is not particularly limited, but for example, it may be between 1 nm and 100 nm, between 5 nm and 50 nm, or between 10 nm and 30 nm. The thickness of the coating layer can be determined, for example, as the average thickness of multiple samples (e.g., 100 or more samples) observed by a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0027] The coating layer may directly coat the electrode active material. Alternatively, the coating layer may indirectly coat the electrode active material. Indirect coating means that a layer not containing the oxide solid electrolyte as defined in this disclosure is placed between the electrode active material and the coating layer. Even if a layer not containing the oxide solid electrolyte is placed between the electrode active material and the coating layer in a portion of the coating active material, if there is a portion where the electrode active material and the coating layer are in direct contact, the coating layer can be considered to directly coat the electrode active material.

[0028] 2. Electrode active material The electrode active material in this disclosure includes, for example, Li, M, and O. M is a metal other than Li (including metalloids), and preferably contains at least Ni. M other than Ni may be a transition metal, or a metal (including metalloids) belonging to groups 13 to 16 of the periodic table. Furthermore, M other than Ni may be one metal or two or more metals. In particular, M other than Ni is preferably at least one of Co, Mn, Al, V, and Fe.

[0029] The molar ratio of Ni to M (Ni / M) may be, for example, 80% or more, 85% or more, or 90% or more. On the other hand, Ni / M may be 100% or less than 100%.

[0030] The electrode active material may contain nonmetallic elements such as P in addition to Li, M, and O. Furthermore, the crystal structure of the electrode active material is not particularly limited, but examples include rock salt layered structures, spinel structures, and olivine structures.

[0031] An example of the composition of an electrode active material is LiNi x Co y Al z O2 (0.80 ≤ x, 0 ≤ y, 0 ≤ z, x + y + z = 1), and LiNi a Co b Mn c One example is O2 (0.80 ≤ a, 0 ≤ b, 0 ≤ c, a + b + c = 1).

[0032] The shape of the electrode active material is usually particulate. Particle size D of the electrode active material. 50 For example, it may be 100 nm or larger, and may also be 1 μm or larger. On the other hand, the particle size D of the electrode active material 50 For example, it may be 10 μm or less, or 5 μm or less.

[0033] 3.Coated active material The coating active material in this disclosure is typically used in batteries. The coating active material may be used as a positive electrode active material or a negative electrode active material in a battery, but the former is preferred.

[0034] Figure 2 is a schematic cross-sectional view illustrating a battery using the coating active material described herein. The battery 20 shown in Figure 2 includes a positive electrode active material layer 11, a negative electrode active material layer 12, an electrolyte layer 13 disposed between the positive electrode active material layer 11 and the negative electrode active material layer 12, a positive electrode current collector 14 for collecting current from the positive electrode active material layer 11, and a negative electrode current collector 15 for collecting current from the negative electrode active material layer 12. In the battery 20, it is preferable that the positive electrode active material layer 11 contains the coating active material described above.

[0035] The positive electrode active material layer contains at least a positive electrode active material and may optionally contain at least one of a conductive additive, a binder, and an electrolyte. The positive electrode active material is preferably the coating active material described above. Examples of conductive additives, binders, and electrolytes include general materials used in batteries. The electrolyte may be a liquid electrolyte (electrolyte solution) or a solid electrolyte, but the latter is preferred. Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes and oxide solid electrolytes.

[0036] The negative electrode active material layer contains at least a negative electrode active material and may optionally contain at least one of a conductive additive, a binder, and an electrolyte. The conductive additive, binder, and electrolyte are as described above. Examples of negative electrode active materials include metallic active materials such as Li and Sn, Si-based active materials, carbon active materials such as graphite, and Li4Ti5O12 Examples of oxide active materials include the following.

[0037] The electrolyte layer contains at least an electrolyte and may contain a binder as needed. The binder and electrolyte are as described above. Here, generally, a battery in which the electrolyte layer contains a solid electrolyte (e.g., an inorganic solid electrolyte) is called a solid battery. A solid battery may be a semi-solid battery or a fully solid battery.

[0038] The positive electrode current collector and the negative electrode current collector can be components commonly used in batteries. Examples of materials for the positive electrode current collector include stainless steel (SUS), aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials for the negative electrode current collector include stainless steel (SUS), copper, nickel, and carbon.

[0039] The method for producing the coated active material is not particularly limited, but the method described in "B. Method for producing the coated active material" is preferred.

[0040] B. Method for producing coated active material Figure 3 is a flowchart illustrating a method for producing the coating active material in this disclosure. In the production method shown in Figure 3, a slurry containing the electrode active material, the oxide solid electrolyte, and a solvent for dissolving the oxide solid electrolyte is prepared (slurry preparation step). Next, the coating layer is formed by a spray-drying method in which the slurry is sprayed with atomized air and dried (coating layer formation step). In this disclosure, the coating conditions are adjusted so that the coating active material described in "A. Coating Active Material" above is obtained. In particular, in the spray-drying method in the coating layer formation step, the gas-liquid ratio is set to 5.0 × 10⁻⁶. -3 Adjust as follows:

[0041] According to this disclosure, the gas-liquid ratio is 5.0 × 10 -3 By adjusting the following, the particle size (D 50 ) can be used to produce a coated active material with a particle size of 5.5 μm or less.

[0042] 1. Slurry preparation process The slurry preparation step is a step of preparing a slurry containing the electrode active material, the oxide solid electrolyte, and a solvent for dissolving the oxide solid electrolyte. The electrode active material and oxide solid electrolyte are the same as those described in "A. Coating Active Material".

[0043] The solvent is not particularly limited as long as it can dissolve the above-mentioned oxide solid electrolyte. For example, water can be used as a solvent.

[0044] The slurry can be prepared, for example, by preparing a coating solution by dissolving the raw materials for an oxide solid electrolyte (e.g., Li source, B source, P source, La source, and O source) in water, and then adding and mixing the electrode active material to the coating solution.

[0045] The Li source is not particularly limited as long as it is an element or compound containing the element Li, but an example is lithium hydroxide (LiOH). The B source is not particularly limited as long as it is an element or compound containing the element B, but an example is boric acid (H3BO3). The P source is not particularly limited as long as it is an element or compound containing the element P, but an example is orthophosphoric acid (H3PO4) and metaphosphoric acid (HPO3). The La source is not particularly limited as long as it is an element or compound containing the element La, but an example is lanthanum oxide (La2O3). The O source is, for example, the element O contained in the element sources mentioned above.

[0046] Furthermore, the solid content concentration in the slurry is not particularly limited, and it is preferable to adjust it as appropriate so that the gas-liquid ratio described later can be obtained. The solid content concentration of the slurry is, for example, 50% by weight or more and 70% by weight or less.

[0047] 2.Coating layer formation process The coating layer formation process is a process of forming a coating layer by a spray-drying method. More specifically, it is a process of forming the coating layer by spraying the slurry together with atomized air and drying it. In particular, in the coating layer formation process in this disclosure, the gas-liquid ratio is 5.0 × 10-3 The following adjustments will be made. Note that the coating layer formation process in this disclosure corresponds to a so-called wet coating process.

[0048] The gas-liquid ratio is 3.0 × 10⁻⁶ -3 It may also be less than or equal to 1.0 × 10 -3 The following is also acceptable: 5.0 × 10 -4 The following may also be true. On the other hand, the gas-liquid ratio may be, for example, 1.0 × 10⁻⁶. -4 That concludes the explanation. The gas-liquid ratio can be determined as the ratio of the water supply rate (L / min) to the atomization air flow rate (L / min).

[0049] The flow rate of atomized air is not particularly limited as long as the above gas-liquid ratio is obtained, but for example it may be 60 L / min or more, 100 L / min, 300 L / min or more, or 1000 L / min or more. On the other hand, the flow rate of atomized air may be 2500 L / min or less, or 2000 L / min or less.

[0050] The water supply rate (L / min) can be calculated, for example, using the following formula. Water supply amount = [Slurry supply rate (L / min)] × [1 - (Solid content concentration (%) / 100)] The water supply rate is not particularly limited as long as the above gas-liquid ratio is achieved, but for example it may be 0.10 L / min or more, 0.50 L / min or more, or 1.0 L / min or more. On the other hand, the water supply rate may be 10 L / min or less, 5.0 L / min or less, or 3.0 L / min or less.

[0051] The powder obtained through the above coating layer formation process may be subjected to calcination. This is because it can increase the crystallinity of the oxide solid electrolyte in the coating layer. The calcination temperature is not particularly limited, but for example, it is between 500°C and 1000°C. The calcination time is not particularly limited, but for example, it is between 30 minutes and 20 hours.

[0052] 3.Coated active material The coated active material produced through the process described above is the same as described in "A. Coated Active Material".

[0053] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0054] [Example 1] (Preparation of coating solution) A coating solution for a coating layer was prepared as follows, containing an oxide solid electrolyte with elements Li, P, B, and O. First, 4.52 g of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries) was dissolved in 191.8 g of deionized water. Next, boric acid (manufactured by Nacalai Tesque) was added and dissolved so that the molar ratio (B / P) was 1.0. Furthermore, lithium hydroxide monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries) was added and stirred so that the molar ratio (Li / (P+B)) was 1.00.

[0055] (Preparation of coated active material) The above coating solution contains an active material (NCA:LiNi 0.81 Co 0.15 Al 0.04 O2; particle size D 50 A slurry was obtained by dispersing particles (2.9 μm). The solid content concentration of the slurry was adjusted by further dilution with deionized water. The obtained slurry was dried using a spray drying apparatus to obtain solid components. The spray drying conditions were set to an air supply temperature of 200°C, and the atomized air flow rate (air flow rate) and water supply amount were as shown in Table 1. The water supply amount was calculated using the formula described above. The obtained solid components were then heat-treated at 200°C for 5 hours in an atmospheric environment. This yielded a coating active material.

[0056] [Examples 2-8 and Comparative Example 1] As shown in Table 1, the coated active material was obtained in the same manner as in Example 1, except that the particle size of the active material and the coating layer formation conditions (spray drying conditions) were changed. The amount of water supplied was adjusted by changing the solid content concentration of the slurry.

[0057] [Table 1]

[0058] [evaluation] (Particle size) For each coated active material, the particle size distribution was measured using "AeroTrac II" manufactured by Microtrac-Bell. Then, D 10 (Particle size at which the cumulative sum becomes 10%), D 50 (Particle size at which the cumulative sum becomes 50%) and D 90 The particle size at which the cumulative sum reaches 90% was calculated. The results are shown in Table 2. In addition, the ratio of particle size before and after coating layer formation and the variation in particle size of the coating active material were calculated from the obtained values. The results are shown in Table 2. Note that the smaller the ratio of particle size before and after coating layer formation, the more suppressed the aggregation of coated particles can be considered. Regarding the variation in particle size, a value closer to 1.0 means that the variation is small.

[0059] Furthermore, the gas-liquid ratio and the D of the coating active material 50 The relationship is shown in Figure 4(a), and the relationship between the gas-liquid ratio and the ratio of particle sizes before and after the formation of the coating layer is shown in Figure 4(b).

[0060] (Coverage) The coverage of each coating active material was measured by X-ray photoelectron spectroscopy (XPS). Specifically, surface elemental analysis of the coating active material was performed using an X-ray photoelectron spectroscopy analyzer (ULVAC-PHI, PHI X-tool). The pass energy was set to 224 eV, and narrow-scan analysis was performed. Subsequently, using analysis software (MultiPak, ULVAC-PHI), the elemental ratios were calculated from the detected intensity values ​​of Li1s, Ni2p3, Co2p3, Al1p, and B1s, and the value of (P+B) / (P+B+Ni+Co+Al) [%] was determined as the coverage. The results are shown in Table 2.

[0061] (Microscopic observation) Images of the coated active material prepared in Example 1 were acquired using a scanning electron microscope (SEM). These are shown in Figure 5.

[0062] (Battery resistance) As described below, evaluation batteries (all-solid-state batteries) having a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer were fabricated using the respective coating active materials of Comparative Example 1 and Examples 1 to 8. A positive electrode slurry was prepared by mixing a coating active material (positive electrode active material), a sulfide solid electrolyte (10LiI-15LiBr-75Li3PS4), a conductive material (VGCF), a binder (SBR), and a dispersion medium (heptane) using an ultrasonic homogenizer. The ratio of positive electrode active material to sulfide solid electrolyte was set to "positive electrode active material / sulfide solid electrolyte = 6 / 4 (volume ratio)". The ratio of conductive material and binder was 3 parts by mass per 100 parts by mass of positive electrode active material, respectively. The positive electrode slurry was coated onto the surface of a positive electrode current collector (Al foil) and dried on a hot plate at 100°C for 30 minutes. This obtained a positive electrode having a positive electrode active material layer and a positive electrode current collector. An all-solid-state battery was fabricated using this positive electrode. For the negative electrode active material, graphite was used, and the same sulfide solid electrolyte as the positive electrode active material layer was used as the solid electrolyte in the negative electrode active material layer and solid electrolyte.

[0063] For each evaluation battery prepared, the open-circuit voltage (OCV) was adjusted to 2.03V. Constant current discharge was then performed, and the battery resistance was measured by dividing the voltage drop over 5 seconds by the current. The discharge current rate was set to 2.5C. Comparative Example 1 was used as the baseline (1.00) for relative evaluation. The results are shown in Table 2.

[0064] [Table 2]

[0065] As shown in Tables 1 and 2 and Figures 4(a) and 4(b), the gas-liquid ratio is 5.0 × 10⁻⁶. -3 By doing the following, aggregation can be suppressed, D 50 Small coated active material was successfully manufactured. Furthermore, it was confirmed that battery resistance could be significantly suppressed when this coated active material was used. In addition, both particle size variation and coating rate were good in the comparative example and the example, and no major differences were observed. In particular, as shown in Figure 5, it was confirmed that the coated active material of Example 1 yielded particles with a more uniform size.

[0066] [Reference example 1] A coating solution containing an oxide solid electrolyte with elements Li, Nb, and O was prepared as follows. 870.4 g of 30% by mass hydrogen peroxide solution was placed in a container, and then 987.4 g of deionized water and 44.2 g of niobium acid (Nb2O5·3H2O (Nb2O5 water content 72%)) were added. Next, 87.9 g of 28% by mass aqueous ammonia was added to the container. By adding aqueous ammonia and stirring, a clear solution was obtained. 10.1 g of lithium hydroxide monohydrate (LiOH·H2O) was added to the obtained clear solution. This yielded a complex solution containing a niobium peroxo complex and lithium ions as a coating solution.

[0067] The coating active material was obtained in the same manner as in Example 1, except that this coating liquid was used and the coating layer formation conditions were changed as shown in Table 3.

[0068] [Reference examples 2~7] Particle size of the active material (D 50 The coating active material was prepared in the same manner as in Example 1, except that the gas-liquid ratio was changed as shown in Table 3.

[0069] For each coated active material obtained in the reference example, the particle size and coating rate were measured in the same manner as described above. The results, along with those for Example 1, are shown in Table 4.

[0070] [Table 3]

[0071] [Table 4]

[0072] As shown in Tables 3 and 4, in Reference Example 1, where the oxide solid electrolyte does not contain P, granulation of the active material was suppressed even when the gas-liquid ratio was increased. Thus, it was confirmed that granulation of the active material is a problem specific to cases where the coating layer contains P. Furthermore, in Reference Examples 2 to 8, the particle size ratio was as low as in the examples, and it was confirmed that granulation itself was suppressed even when the particle size of the active material was increased. Also, D 50 Even when using an active material with a relatively large value, the gas-liquid ratio is 5.0 × 10 -3 By doing the following, the D of the coating active material 50 It was confirmed that the ratio could be reduced. This is presumed to be because a thin coating layer could be formed by reducing the gas-liquid ratio. [Explanation of Symbols]

[0073] 1...electrode active material 2...Covering layer 10...Coated active material 11...Cathode active material layer 12...Negative electrode active material layer 13...electrolyte layer 14...Positive electrode current collector 15...Negative electrode current collector 20...battery

Claims

1. A coated active material comprising an electrode active material and a coating layer covering the electrode active material, The coating layer contains an oxide solid electrolyte containing Li, P and O elements, The particle size (D) of the coated active material ５０ ) is 5.5 μm or less, A coating active material wherein the oxide solid electrolyte further contains element B or element La.

2. The particle size (D ５０ The coated active material according to claim 1, wherein the diameter of the ) is 1.0 μm or larger.

3. A method for producing a coated active material, The coating active material comprises an electrode active material and a coating layer that covers the electrode active material, wherein the coating layer contains an oxide solid electrolyte containing Li, P and O elements, and the particle size (D 50) of the coating active material is 5.5 μm or less. The aforementioned manufacturing method is A slurry preparation step involves preparing a slurry containing the electrode active material, the oxide solid electrolyte, and a solvent for dissolving the oxide solid electrolyte. The process includes a coating layer formation step, in which the coating layer is formed by a spray-drying method in which the slurry is sprayed together with atomized air and dried, The gas-liquid ratio in the aforementioned spray drying method is 5.0 × 10 －３ The following is a method for producing a coated active material.

4. The method for producing a coated active material according to claim 3, wherein the oxide solid electrolyte further contains element B or element La.

5. The method for producing a coated active material according to claim 3, wherein the flow rate of the atomized air is 60 L / min or more.

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