Battery

Abstract

To provide a battery that is good in capacity and suppressed in deterioration of capacity.SOLUTION: In the present disclosure, there is provided a battery including a cathode active material layer, an anode active material layer, and an electrolyte layer disposed between the cathode active material layer and the anode active material layer. One of the cathode active material layer and the anode active material layer contains an active material having a composition of LiNiO2, and when X-ray diffraction measurement using CuKα rays is performed at a potential of 3.5 V(vsLi+ / Li), the active material has a peak derived from a plane (003) and a peak derived from a plane (104), and a ratio (I(003) / I(104)) of the peak intensity I(003) derived from the plane (003) to the peak intensity I(104) derived from the plane (104) is greater than 1.575.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to batteries. [Background technology]

[0002] In recent years, there has been active development of batteries. For example, in the automotive industry, development of batteries for use in electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), and hybrid electric vehicles (HEVs) is underway. In addition, development of materials for use in these batteries is also underway.

[0003] For example, Patent Document 1 discloses a lithium secondary battery having a positive electrode active material made of LiNiO2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-215773 Summary of the Invention [Problem to be solved by the invention]

[0005] LiNiO2 is known to be used as an active material in batteries. + and Ni 2+ Because the ionic radii of LiNiO2 are similar to those of LiNiO2, there is a risk of cation mixing. Therefore, batteries using LiNiO2 may experience a decrease in capacity with charging and discharging. Furthermore, there is room for further improvement in increasing the capacity of batteries using LiNiO2.

[0006] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a battery having a good capacity and in which deterioration of the capacity is suppressed. [Means for solving the problem]

[0007] [1] A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, one of the positive electrode active material layer and the negative electrode active material layer contains an active material having a composition of LiNiO2; The above active material is 3.5V (vs Li + When X-ray diffraction measurement was performed using CuKα radiation at a potential of 1000 nm / Li, it had a peak due to the (003) plane and a peak due to the (104) plane, and A battery in which the ratio (I(003) / I(104)) of the peak intensity I(003) attributable to the (003) plane to the peak intensity I(104) attributable to the (104) plane is greater than 1.575.

[0008] [2] The battery according to [1], wherein the I(003) / I(104) is 2.490 or less.

[0009] [3] The battery according to [1] or [2], wherein the I(003) / I(104) is 1.610 or more.

[0010] [4] The active material contains a compound containing an S element inside or on the surface thereof, The battery according to any one of [1] to [3], wherein the proportion of the S element in the active material is 400 ppm or more and 1000 ppm or less.

[0011] [5] The battery according to any one of [1] to [4], wherein the positive electrode active material layer contains the active material. [Effects of the Invention]

[0012] The battery of the present disclosure has the effect of providing a good capacity and suppressing deterioration of the capacity. [Brief explanation of the drawings]

[0013] [Figure 1]FIG. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. [Figure 2] 1 shows the results of XRD measurement of the active materials obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] The battery according to the present disclosure will be described in detail below.

[0015] FIG. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. Note that FIG. 1 is a schematic illustration of the battery according to the present disclosure, and the size and shape of each part are appropriately exaggerated for ease of understanding. The battery 10 shown in FIG. 1 has a positive electrode active material layer 1, a negative electrode active material layer 2, and an electrolyte layer 3 disposed between the positive electrode active material layer 1 and the negative electrode active material layer 2, and one of the positive electrode active material layer 1 and the negative electrode active material layer 2 contains an active material having a composition of LiNiO2. In particular, in the present disclosure, the active material has a voltage of 3.5 V (vs Li + When X-ray diffraction measurement was performed using CuKα radiation at a potential of 1000 Å (0.15 Å) / Li, it was found that there were peaks attributable to the (003) plane and peaks attributable to the (104) plane, and the ratio of the peak intensity I(003) attributable to the (003) plane to the peak intensity I(104) attributable to the (104) plane (I(003) / I(104)) was greater than 1.575.

[0016] In the battery of the present disclosure, the positive electrode active material layer or the negative electrode active material layer contains an active material having a composition of LiNiO2, and the active material has a voltage of 3.5 V (vs Li + When X-ray diffraction measurement was performed using CuKα radiation at a potential of 0.05V / Li, it showed a peak due to the (003) plane and a peak due to the (104) plane, and the ratio of the peak intensity I(003) due to the (003) plane to the peak intensity I(104) due to the (104) plane (I(003) / I(104)) was greater than 1.575. This resulted in a battery with good capacity and suppressed capacity degradation.

[0017] LiNiO2 is known as a compound with the O3 structure. The O3 structure means that Li occupies the octahedral site in the oxide, and there are three types of oxide layers with different oxygen positions in the unit lattice. On the other hand, as mentioned above, Li + and Ni 2+ Since the ionic radii of these elements are close to each other, there is a risk of cation mixing occurring. This is particularly likely when the ratio of Ni to Li is high, as in LiNiO2. Cation mixing can cause deterioration of the active material, such as changes in the crystalline structure of the active material.

[0018] In contrast, the active material contained in the battery of the present disclosure is 3.5V (vs Li + At a potential of 3.5V (Li / Li), the ratio of the peak intensity I(003) attributable to the (003) plane to the peak intensity I(104) attributable to the (104) plane (I(003) / I(104)) is greater than 1.575, thereby suppressing cation mixing. For example, an academic paper (T. Ohzuku, A. Ueda, M. Nagayama, Y. Iwakoshi, and H. Komori, Electrochim. Acta, 38, 1159 (1993)) states that when XRD measurements are performed on active materials immediately after fabrication, if the I(003) / I(104) ratio is 1.2 or greater, the sample exhibits low cation mixing. Based on this knowledge, the inventors conducted extensive research and discovered that if the I(003) / I(104) ratio at 3.5V, near the plateau region of LiNiO2, is greater than a predetermined value, cation mixing is suppressed and high capacity is achieved, leading to the completion of the present invention.

[0019] 1.Active material In the battery of the present disclosure, one of the positive electrode active material layer and the negative electrode active material layer contains an active material having a composition of LiNiO2.

[0020] The active material in this disclosure has a voltage of 3.5V (vs. Li +When X-ray diffraction measurement (XRD measurement) using CuKα radiation is performed at a potential of 0.05 V / Li, peaks originating from the (003) plane and the (104) plane are observed. The positions of the peaks originating from the (003) plane and the (104) plane are typically 2θ = 18.7° and 44.4°, respectively. These peak positions may vary within a range of ±2.0°, ±1.0°, ±0.5°, ±0.3°, or ±0.1°.

[0021] In the active material of the present disclosure, in the XRD measurement, the ratio of I(003) to I(104) (I(003) / I(104)) is greater than 1.575, where I(003) is the peak intensity attributable to the (003) plane and I(104) is the peak intensity attributable to the (104) plane. I(003) / I(104) may be 1.61 or greater, 1.70 or greater, or 1.80 or greater. Furthermore, I(003) / I(104) may be 2.49 or less, 2.20 or less, or 2.00 or less.

[0022] The I(003) / I(104) ratio can be adjusted by changing the ratio of Li to Ni (Li ratio) in the active material, for example. The Li ratio is, for example, 1.01 or more and 1.07 or less.

[0023] Furthermore, when the active material of the present disclosure is subjected to XRD measurement, it may have characteristic peaks in addition to the peaks attributable to the (003) plane and the (104) plane. The positions of the characteristic peaks may be at 2θ=36.6°, 38.3°, 48.7°, 58.6°, and 64.6°. The positions of these peaks may vary within a range of ±2.0°, ±1.0°, ±0.5°, ±0.3°, or ±0.1°.

[0024] Furthermore, the active material of the present disclosure may or may not contain a compound containing elemental sulfur (sulfur compound) on the surface or inside. It is believed that the sulfur compound can suppress the reaction between the active material and the electrolyte (or decomposition products of the electrolyte), thereby further suppressing degradation of the active material. An example of the sulfur compound is Li2SO4. As described in the Examples below, when a precursor is prepared by coprecipitation using NaOH and NiSO4, Li2SO4 is believed to be generated by the reaction of sulfate ions remaining in the precursor with lithium hydroxide (lithium hydroxide monohydrate). The proportion of elemental sulfur in the active material is, for example, 10 ppm or more, 100 ppm or more, 300 ppm or more, or even 500 ppm or more. On the other hand, the proportion of elemental sulfur is, for example, 1000 ppm or less. The proportion of elemental sulfur can be determined by ICP (Inductive Coupled Plasma) emission spectroscopy (ICP measurement). When the proportion of the S element is less than 10 ppm, the active material can be considered to contain substantially no S element.

[0025] The active material in the present disclosure may be in the form of, for example, particles, which may be primary particles or secondary particles formed by aggregation of primary particles.

[0026] Average particle diameter of the active material (D 50 ) is not particularly limited, but is, for example, 0.01 μm or more and 100 μm or less. 50 ) refers to the cumulative 50% particle size in the volume-based particle size distribution measured by a laser diffraction particle size analyzer.

[0027] The active material of the present disclosure may be used as either a positive electrode active material or a negative electrode active material in a battery, but the former is preferred. Therefore, the following describes a battery containing the above-mentioned active material as a positive electrode active material.

[0028] 2.Cathode active material layer The positive electrode active material layer in the present disclosure contains at least a positive electrode active material. The positive electrode active material layer preferably contains the active material described above as the positive electrode active material.

[0029] The positive electrode active material is the same as that described in "1. Active material." The proportion of the positive electrode active material in the positive electrode active material layer is, for example, 30% by weight or more and 99% by weight or less.

[0030] The positive electrode active material layer may further contain at least one of an electrolyte, a conductive material, and a binder. The electrolyte is the same as that described in "4. Electrolyte Layer." Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fiber, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of binders include rubber-based binders and fluoride-based binders.

[0031] The thickness of the positive electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

[0032] 3.Negative electrode active material layer The negative electrode active material layer in the present disclosure contains at least a negative electrode active material. The negative electrode active material layer may further contain at least one of an electrolyte, a conductive material, and a binder. The electrolyte, the conductive material, and the binder are the same as those described in "2. Positive electrode active material layer."

[0033] Examples of the negative electrode active material include Li-based active materials such as Li and Li alloys, Si-based active materials, carbon active materials such as graphite, and Li4Ti5O 12 Examples of oxide active materials include the above. Among them, the negative electrode active material is preferably a Si-based active material, because this allows for achieving a high capacity battery. The Si-based active material is an active material containing Si as the main component. The Si-based active material may be simple Si, a Si alloy, or a Si oxide.

[0034] The Si-based active material may have a diamond-type crystalline phase, a clathrate I-type crystalline phase, or a clathrate II-type crystalline phase. In the clathrate I-type or II-type crystalline phase, multiple Si elements form a polyhedron (cage) containing pentagons or hexagons. This polyhedron has spaces inside that can encapsulate metal ions such as Li ions, thereby suppressing volume changes due to charge and discharge.

[0035] The Si-based active material may have voids inside. The proportion of voids (porosity) is not particularly limited, but is, for example, 4% or more and 40% or less. The presence of voids in the Si-based active material and the porosity can be confirmed by observation with a scanning electron microscope (SEM). The voids can suppress volume changes in the Si-based active material caused by charging and discharging the battery.

[0036] The negative electrode active material may be in the form of particles, for example. 50 ) is not particularly limited, but may be, for example, 10 nm or more, or may be 100 nm or more. On the other hand, the average particle diameter (D 50 ) is, for example, 50 μm or less, and may be 20 μm or less. 50 The above is as stated above.

[0037] The thickness of the negative electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

[0038] 4. Electrolyte layer The electrolyte layer is a layer disposed between the positive electrode active material layer and the negative electrode active material layer, and contains at least an electrolyte.

[0039] The electrolyte may be, for example, a liquid electrolyte (electrolyte). The electrolyte may be a conventionally known electrolyte used in lithium ion batteries. Specifically, the electrolyte may contain a lithium salt such as LiPF6 and a non-aqueous solvent such as ethylene carbonate (EC), dimethyl carbonate (DMC), or ethyl methyl carbonate (EMC). When the electrolyte contains an electrolytic solution, the electrolyte layer may be a layer in which the separator is impregnated with the electrolytic solution. The separator may be a conventionally known member.

[0040] The electrolyte may be a solid electrolyte, such as an inorganic solid electrolyte, such as a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte.

[0041] The electrolyte layer may contain a binder as needed. The binder is the same as that described in "2. Positive Electrode Active Material Layer." The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0042] 5. Other configurations The battery of the present disclosure typically includes a positive electrode current collector that collects current from the positive electrode active material layer and a negative electrode current collector that collects current from the negative electrode active material layer. Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, and carbon. Examples of materials for the negative electrode current collector include stainless steel, copper, nickel, and carbon.

[0043] 6.Battery The capacity retention rate (discharge capacity at the 30th cycle / discharge capacity at the 1st cycle) of the battery in the present disclosure is, for example, 70% or more, or may be 75% or more, or 80% or more, or 85% or more, or may be 90% or more.

[0044] The type of battery in the present disclosure is typically a lithium-ion battery. The battery in the present disclosure may be a primary battery or a secondary battery, with secondary batteries being preferred. This is because they can be repeatedly charged and discharged, making them useful, for example, as automotive batteries. The battery in the present disclosure is typically a liquid-based battery whose electrolyte layer contains an electrolytic solution. Alternatively, the battery in the present disclosure may be a solid-state battery whose electrolyte layer contains a solid electrolyte (particularly an inorganic solid electrolyte). Examples of solid-state batteries include all-solid-state batteries and semi-solid-state batteries.

[0045] Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, it is preferable to use the battery as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices.

[0046] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0047] [Example 1] (Preparation of positive electrode active material) A reaction vessel with a temperature adjusted to 30°C was prepared. An 8 mol / L aqueous sodium hydroxide solution was used to maintain the reaction solution in the reaction vessel at pH 11.5. A solution containing a solid component (nickel hydroxide) was obtained by a crystallization method in which a nickel sulfate aqueous solution and a 28% by mass aqueous ammonia solution were added dropwise. The solution was subjected to suction filtration to separate the filtrate and the solid component, and the solid component was recovered and washed with water. The solution was then immersed in a 1 mol / L aqueous sodium hydroxide solution for 15 minutes, and suction filtration was again performed to recover the solid component. The solution was then left to dry overnight in a 120°C air dryer. This yielded a precursor (nickel hydroxide).

[0048] The precursor (nickel hydroxide) and lithium hydroxide monohydrate were weighed out so that the Li to Ni ratio was 1.02, and mixed in a mortar. The mixture was heated to 485°C at a rate of 10°C / min in an oxygen atmosphere using an electric furnace, and pre-baked for 5 hours. Then, the mixture was baked at 680°C for 20 hours. The mixture was then cooled to room temperature in the furnace and crushed. This produced a lithium nickel-containing oxide. A test battery, described below, was fabricated using this lithium nickel-containing oxide as the positive electrode active material.

[0049] (Preparation of evaluation battery) A positive electrode active material, a conductive additive, and a binder were mixed in a weight ratio of 90:5:5 to obtain a positive electrode slurry. The positive electrode slurry was applied to a positive electrode current collector (aluminum foil) and dried with hot air at 80°C for 30 minutes. It was then punched out to a diameter of 16 mm, pressed, and further vacuum-dried at 120°C. This resulted in a positive electrode. A 2032-type coin battery (evaluation battery) was fabricated using the obtained positive electrode and Li metal as a counter electrode. The electrolyte used was a mixed solvent containing 1M LiPF6, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).

[0050] [Examples 2 to 4, Comparative Example 1] Positive electrode active materials and test batteries were produced in the same manner as in Example 1, except that at least one of the cleaning method and the Li ratio in producing the precursor was changed as shown in Table 1.

[0051] [Example 5] In the method shown in Example 1, a lithium nickel-containing oxide was synthesized by changing the cleaning method and Li ratio in the preparation of the precursor as shown in Table 1. The synthesized lithium nickel-containing oxide was then immersed in distilled water for 1 minute and further washed. Thereafter, the lithium nickel-containing oxide was recovered by suction filtration and dried overnight in a vacuum dryer at 120°C. A test battery was produced in the same manner as in Example 1, using the dried lithium nickel-containing oxide as the positive electrode active material.

[0052] [Table 1]

[0053] [evaluation] (XRD measurement) Each test battery was charged to 4.4 V at a Li potential and discharged to 3.5 V at a Li potential. The test battery was then disassembled to remove the positive electrode active material layer. The positive electrode active material was sealed in a non-exposure jig, and an XRD pattern of the positive electrode active material was obtained using an X-ray diffractometer. From the obtained XRD pattern, the peak intensity I(003) of the (003) plane and the peak intensity I(104) of the (104) plane were obtained, and I(003) / I(104) was calculated. The results are shown in Table 2. The XRD patterns of Example 1 and Comparative Example 1 are shown in FIG. 2.

[0054] (Cycle test) For each evaluation battery, 4.4 to 2.8 V (vs Li +A cycle test was conducted under conditions of 0.05C / Li and 25°C. The first three cycles were charged and discharged at a C rate of 0.05C, and then the next 30 cycles were charged and discharged at a C rate of 0.2C. The capacity (discharge capacity) was measured at the first, third, and 30th cycles, and the capacity retention rate (%) at the 3rd and 30th cycles was calculated. The results are shown in Table 2.

[0055] (ICP measurement) The concentrations of S element (S residues) were measured by ICP measurement for the positive electrode active materials produced in Examples 1 to 5 and Comparative Example 1. The results are shown in Table 2.

[0056] [Table 2]

[0057] As shown in FIG. 2, both Example 1 and Comparative Example 1 exhibited peaks characteristic of LiNiO2. However, as shown in Table 2, Example 1 had a higher peak intensity ratio and exhibited better initial capacity and capacity retention. Similarly, the other Examples also exhibited good initial capacity and capacity retention. Thus, it was confirmed that batteries using the active material of the present disclosure exhibited good capacity and suppressed capacity degradation. It was also confirmed that the amount of residual sulfur could be adjusted by the method of washing the precursor and active material. [Explanation of symbols]

[0058] 1...Cathode active material layer 2...Negative electrode active material layer 3...electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...battery

Claims

1. A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, One of the positive electrode active material layer and the negative electrode active material layer is LiNiO ２ The active material has a composition of The active material is 3.5 V (vs. Li ＋ When X-ray diffraction measurement was performed using CuKα radiation at a potential of 1000 nm / Li), the sample had a peak due to the (003) plane and a peak due to the (104) plane, and A battery in which the ratio (I(003) / I(104)) of the peak intensity I(003) attributable to the (003) plane to the peak intensity I(104) attributable to the (104) plane is greater than 1.

575.

2. 2. The battery of claim 1, wherein the I(003) / I(104) is 2.49 or less.

3. 2. The battery of claim 1, wherein the I(003) / I(104) is 1.61 or greater.

4. the active material contains a compound containing an S element inside or on a surface thereof, 2. The battery according to claim 1, wherein the content of the S element in the active material is 400 ppm or more and 1000 ppm or less.

5. The battery according to claim 1 , wherein the positive electrode active material layer contains the active material.

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