Positive electron active material for nonaqueous electrolyte secondary battery

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, and particularly when used as a positive electrode material, it is possible to improve thermal stability without impairing the initial capacity of the battery. Regarding positive electrode active material for batteries.

【0002】

[Conventional technology]

In recent years, with the spread of mobile devices such as mobile phones and notebook computers, the development of small and lightweight secondary batteries having a high energy density has been strongly desired. As such, there is a lithium ion secondary battery that uses lithium, a lithium alloy, a metal oxide, or carbon as a negative electrode, and research and development are being actively carried out.

【0003】

Lithium composite oxides, especially lithium cobalt composite oxides (LiCoO), which are relatively easy to synthesize₂) Is used as the positive electrode material, and since a high voltage of 4V class can be obtained, it is expected as a battery having a high energy density and is being put into practical use. Batteries using lithium cobalt composite oxides have been developed in many ways to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained.

【0004】

However, since lithium cobalt composite oxide uses a rare and expensive cobalt compound as a raw material for the positive electrode active material, it causes an increase in the cost of the positive electrode active material and further increases the cost of the battery, and improvement of the positive electrode active material is desired. It is rare. Reducing the cost of the positive electrode active material and making it possible to manufacture a cheaper lithium-ion secondary battery has great industrial significance in terms of weight reduction and miniaturization of mobile devices that are currently in widespread use.

【0005】

A new material for the positive electrode active material for lithium-ion secondary batteries is a lithium-manganese composite oxide (LiMn) that uses manganese, which is cheaper than cobalt.₂O₄) And lithium nickel composite oxide using nickel (LiNiO)₂) Can be mentioned.

【0006】

Lithium-manganese composite oxide can be said to be a promising alternative to lithium-cobalt composite oxide because it is inexpensive as a raw material and has excellent thermal stability as a positive electrode material, but its theoretical capacity is approximately that of lithium-cobalt composite oxide. There is only about half of it, and it has the drawback that it is difficult to meet the increasing demand for higher capacity lithium-ion secondary batteries.

【0007】

On the other hand, lithium nickel composite oxides show lower electrochemical potential than lithium cobalt composite oxides, so higher capacity can be expected, and they show high battery voltage like cobalt oxides, so they are being actively developed. ing. However, when a lithium ion secondary battery is manufactured using a lithium nickel composite oxide synthesized purely from nickel as a positive electrode active material, the cycle characteristics are inferior to those of a cobalt type battery, and it can be used and stored in a high temperature environment. It is relatively easy to impair battery performance.

【0008】

In order to solve such a drawback, a lithium nickel composite oxide in which a part of nickel is replaced with another metal, for example, Japanese Patent Application Laid-Open No. 8-213015, improves the self-discharge characteristics and cycle characteristics of the lithium ion secondary battery. For the purpose of_xNi_aCo_{b b}M_cO₂(0.8 x 1.2, 0.01 a 0.99, 0.01 b 0.99, 0.01 c 0.3, 0.8 a + b + c 1.2, M is selected from Al, V, Mn, Fe, Cu and Zn. Lithium-nickel composite oxides represented by at least one element) have been proposed.

【0009】

Further, in Japanese Patent Application Laid-Open No. 8-45509, Li is used as a positive electrode active material that can maintain good battery performance when stored and used in a high temperature environment._wNi_xCo_yB_zO₂Lithium-nickel composite oxides represented by (0.05 w 1.10, 0.5 x 0.995, 0.005 z 0.20, x + y + z = 1) have been proposed.

【0010】

Further, Japanese Patent Application Laid-Open No. 8-321299 proposes a lithium-containing composite oxide in which 5 at% or less of nickel is replaced with gallium for the purpose of improving cycle characteristics and overcharge resistance.

【0011】

However, the lithium nickel composite oxide obtained by the conventional manufacturing methods such as these has a higher charge capacity and discharge capacity than the lithium cobalt composite oxide, and the cycle characteristics are improved, but the battery is in a fully charged state. If left in a high temperature environment, decomposition with oxygen release starts from a lower temperature than the lithium cobalt composite oxide, and as a result, the internal pressure of the battery rises, and in the worst case, the battery explodes. Have a risk.

【0012】

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. 5-242891 aims to improve the thermal stability of the positive electrode material of a lithium ion secondary battery, and Li_aM_{b b}Ni_cCo_dO_e(M is at least one metal selected from the group consisting of Al, Mn, Sn, In, Fe, V, Cu, Mg, Ti, Zn, Mo, and 0 <a <1.3, 0.02 b 0.5. , 0.02 d / c + d 0.9, 1.8 <e <2.2, b + c + d = 1)), a lithium-containing composite oxide has been proposed. However, if nickel is replaced with an amount of M element that is effective for improving thermal stability, there is a problem that the initial capacity, which is the most important for battery performance, is greatly reduced.

【0013】

In this way, as previously reported, a non-aqueous electrolyte secondary battery using a lithium nickel composite oxide in which a part of nickel is replaced with another element as a positive electrode active material in order to improve thermal stability. Although it certainly has the effect of improving thermal stability, it has a problem that the initial capacitance is reduced by the amount of replacement.

【0014】

[Problems to be Solved by the Invention]

The present invention has been made by paying attention to such a problem, and an object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery having high thermal stability without sacrificing the initial capacity. To provide.

【0015】

[Means for solving problems]

When lithium nickel composite oxide is considered as a positive electrode active material, charging and discharging are performed by desorption and insertion of lithium. When fully charged at about 200mAh / g, LiNiO₂About 70% of lithium is desorbed from. That is, Li_0.3NiO₂At this time, part of nickel is trivalent and tetravalent. Tetravalent nickel is extremely unstable thermally, and easily releases oxygen at high temperatures to become divalent (NiO).

【0016】

The thermal behavior of the positive electrode active material can be evaluated by measuring the differential scanning calorimetry of the charged positive electrode material in the presence of the electrolytic solution and observing the calorific value thereof. In addition, by investigating the generated gas species using mass spectrometry, it is possible to consider the thermal behavior more concretely.

【0017】

The reason why the lithium nickel composite oxide is inferior in thermal stability as a positive electrode material is that the decomposition start temperature at which oxygen is released and decomposed is lower than that of the lithium cobalt composite oxide, and the oxygen released at this time is different from that of the electrolytic solution. It is thought that the cause is that the reaction causes a combustion reaction, and that nickel itself acts as a catalyst to promote the decomposition reaction of the electrolytic solution.

【0018】

Therefore, in order to improve the thermal stability of the lithium nickel composite oxide as a positive electrode material, a method of improving the lithium nickel composite oxide from the aspect of composition to raise the decomposition start temperature can be considered.

【0019】

That is, since tetravalent nickel is thermally unstable as described above, the decomposition start temperature is obtained by dissolving an element that lowers the valence of nickel in the lithium nickel composite oxide. Can be raised. Alternatively, the decomposition start temperature can be raised by a method of solid-solving a stable element whose valence does not easily change. In either method, the decomposition start temperature accompanied by oxygen release can be shifted to a higher temperature side, and as a result, the thermal stability of the lithium nickel composite oxide as a positive electrode material is increased.

【0020】

However, with these methods, as a result, lithium cannot be extracted from the lithium-nickel composite oxide to a certain extent or more, and as a result of insufficient desorption of lithium, capacity is inevitably sacrificed. That is, an increase in the thermal stability of the lithium nickel composite oxide as a positive electrode material is accompanied by a reduction in the amount of lithium extracted to a certain potential.

【0021】

From the viewpoint of the thermal stability of the battery, not only the thermal stability of the positive electrode active material itself, improvement can be requested other than raising the decomposition start temperature of the positive electrode active material.

【0022】

Lithium-nickel composite oxide is inferior in thermal stability because oxygen released by decomposition reacts (combusts) with the electrolytic solution as described above, so even if the decomposition start temperature is the same, It can be said that if the amount of oxygen released is small, the reaction with the electrolytic solution becomes mild and the thermal stability is improved.

【0023】

From this point of view, the present inventors have conducted various studies on the thermal stability of a battery using a lithium-nickel composite oxide as a positive electrode material, and as a result, instead of substituting a part of nickel with another element, It has been found that a non-aqueous electrolyte secondary battery having excellent thermal stability can be obtained by adding a compound having an ability to absorb oxygen (hereinafter referred to as an oxygen absorbing compound), and the present invention has been completed.

【0024】

In the first aspect of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, the main component is LiNi._1-xM_xO₂(However, M is at least one metal element selected from the group consisting of Co, Mn, Fe, Cu, Zn, Mg, Ti, Al and Ga, and 0.2> x 0). It is a Ni composite oxide and further contains an oxygen absorbing compound.

【0025】

When adding the oxygen absorbing compound, it is necessary to determine the addition amount according to the oxygen absorption capacity, and if the oxygen absorption capacity is sufficiently large, the addition amount can be sufficiently reduced. Even if the addition amount is increased more than necessary, the initial capacity per mass is reduced by the mass, and the effect on the thermal stability of the battery is hardly changed.

【0026】

As a result of deepening the research by the present inventors, it was found that the oxygen absorbing compound is not desirable because the decrease in the initial volume per mass becomes large when the molar ratio of nickel and element M exceeds 2%. ..

【0027】

That is, in the second aspect of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, the molar ratio of the oxygen absorbing compound to the total of nickel and element M is 2% or less.

【0028】

Further, as a third aspect of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, the oxygen absorbing compound is one or more selected from vanadium compounds, indium compounds, tin compounds and tantalum compounds. However, the form of existence may differ between the time of blending and the positive electrode active material.

【0029】

The positive electrode active material according to the present invention is LiNiO, which is inferior in thermal stability.₂Of course, it is effective even if it is used, but in order to improve the cycle characteristics, a part of Ni is replaced with another element such as Co, and in order to improve the conductivity, a part of Ni is Mg. It is also possible to replace it with another element such as. Further, by substituting a part of Ni with another element such as Mn, Ti, Al, Ga, the positive electrode active material itself has a thermal stability effect, and a positive electrode active material having further excellent thermal stability can be obtained. be able to. In these cases, the substitution rate is less than 0.2 in molar ratio.

【0030】

BEST MODE FOR CARRYING OUT THE INVENTION

The positive electrode active material of the present invention is a lithium nickel composite oxide containing a compound having an ability to absorb oxygen (oxygen absorbing compound), and is used as a positive electrode active material of a lithium ion secondary battery. As a result, the thermal stability can be improved with almost no decrease in the initial capacity of the battery.

【0031】

Hereinafter, an embodiment of the present invention will be described in detail with reference to suitable drawings.

【0032】

[Example]

(Example 1) Commercially available lithium hydroxide monohydrate and a composite hydroxide solidly dissolved in a molar ratio of nickel, cobalt and aluminum at a molar ratio of 83:14: 3 are mixed with lithium and nickel + cobalt + aluminum. Each was weighed so that the molar ratio was 1.03: 1.00, and the mixture was thoroughly mixed. This mixed powder has an oxygen flow rate of 3000 cm.³Temporarily bake at 350 ° C for 2 hours in an air flow of / min, then bake at 750 ° C for 20 hours, cool to room temperature, and LiNi._0.83Co_0.14Al_0.03O₂Got

【0033】

A vanadium compound was used as the oxygen absorbing compound. That is, commercially available lithium hydroxide monohydrate was dissolved in pure water, and vanadium pentoxide was added and dissolved so that the molar ratio of lithium to vanadium was 3: 1. The LiNi was added to this aqueous solution so that the molar ratio of vanadium to nickel + cobalt + aluminum was 0.010: 1.00._0.83Co_0.14Al_0.03O₂Was added, heated and stirred, and dried. The obtained dried product has an oxygen flow rate of 3000 cm.³It was fired at 750 ° C. for 20 hours in an air stream of / min and cooled to room temperature to obtain a positive electrode active material composed of a vanadium-containing lithium nickel composite oxide.

【0034】

The obtained positive electrode active material was analyzed by powder X-ray diffraction (manufactured by Rigaku Denki Co., Ltd., model RAD-γVB) using Cu Kα rays. Li as an oxygen absorber₃VO₄The peak of was confirmed. The lattice constant of the lithium nickel composite oxide calculated from the X-ray diffraction pattern is almost the same as the lattice constant of the lithium nickel composite oxide before the addition of vanadium, and vanadium is dissolved in the lithium nickel composite oxide. It was presumed not. When the composition of the positive electrode active material was analyzed, the molar ratio of vanadium to nickel + cobalt + aluminum was 0.01: 1.00, and considering that vanadium was not solid-dissolved, oxygen to the lithium nickel composite oxide was taken into consideration. Li as an absorbent₃VO₄It can be said that the molar ratio of was 1%.

【0035】

Using the obtained positive electrode active material, a battery was prepared as follows, and the charge / discharge capacity was measured.

【0036】

5% by mass of acetylene black and 8% by mass of PVDF (polyvinylidene fluoride) were mixed with 87% by mass of the positive electrode active material powder, and NMP (n-methylpyrrolidone) was added to form a paste. This is made into 20 μm thick aluminum foil, and the mass of the active material after drying is 0.025 g / cm.²It was applied so as to be, vacuum dried at 120 ° C., and punched into a 1 cmφ disk shape to obtain a positive electrode. Lithium metal as the negative electrode, 1M LiClO as the electrolyte₄An equal mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) using the solid salt as a supporting salt was used. A 2032 type coin battery as shown in Fig. 1 was produced in a glove box with an Ar atmosphere in which the dew point was controlled at -80 ° C by impregnating a separator made of polyethylene with an electrolytic solution. The prepared battery is left to stand for about 24 hours, and after the OCV stabilizes, the current density with respect to the positive electrode is 0.5 mA / cm.²A charge / discharge test was conducted with a cutoff voltage of 4.3-3.0 V. Table 1 shows the discharge capacity (initial capacity) per mass of the obtained first cycle.

【0037】

In addition, another battery was prepared by the same method and charged to 196 mAh / g with the current density per mass of the positive electrode set to 6 mA / g. After charging is completed, this battery is disassembled, and 1M of LiClO is used as an electrolytic solution for 2.4 mg of the positive electrode material taken out.₄2.0 mg of an equal amount mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) using the solid salt as a supporting salt was added and sealed in a closed aluminum container, and differential scanning calorimetry was performed. In addition, TG-MS measurement (manufactured by MacScience, model IG-DTA 2020s) of the extracted positive electrode material was carried out, and the gas generated by heating was investigated.

【0038】

The measurement results are shown in Table 1, Fig. 2 and Fig. 3.

【0039】

(Example 2) A composite hydroxide having a molar ratio of nickel, cobalt, and aluminum dissolved at 83: 14: 3 was added to a 30% aqueous ammonia solution in which vanadium pentoxide was dissolved, and vanadium, nickel, cobalt, and aluminum were added. The mixture was charged so that the molar ratio was 0.01: 1.00, heated and stirred, and dried. The obtained dried product and commercially available lithium hydroxide monohydrate were weighed so that the molar ratio of lithium to nickel + cobalt + aluminum was 1.060: 1.000, and the mixture was thoroughly mixed. This mixed powder has an oxygen flow rate of 3000 cm.³After calcining at 350 ° C for 2 hours in an air stream of / min, calcining at 750 ° C for 20 hours and cooling to room temperature, a positive electrode active material composed of a lithium nickel composite oxide to which vanadium was added was obtained. Obtained.

【0040】

The obtained positive electrode active material was analyzed by powder X-ray diffraction using Cu Kα rays. As a result, in addition to the lithium nickel composite oxide attributed to hexagonal crystals, Li as an oxygen absorber₃VO₄The peak of was confirmed. The lattice constant of the lithium nickel composite oxide calculated from the X-ray diffraction pattern is almost the same as the lattice constant of the lithium nickel composite oxide before the addition of vanadium, and vanadium is dissolved in the lithium nickel composite oxide. It was presumed not. When the composition of the positive electrode active material was analyzed, the molar ratio of vanadium to nickel + cobalt + aluminum was 0.01: 1.00, and considering that vanadium was not solid-dissolved, oxygen to the lithium nickel composite oxide was taken into consideration. Li as an absorbent₃VO₄It can be said that the molar ratio of was 1%.

【0041】

The initial capacitance measurement, differential scanning calorimetry, and TG-MS measurement were performed in the same manner as in Example 1. The measurement results are shown in Table 1, Fig. 2 and Fig. 4.

【0042】

(Example 3) Examples except that the molar ratio of lithium and nickel + cobalt + aluminum is 1.090: 1.000 so that the molar ratio of vanadium and nickel + cobalt + aluminum is 0.02: 1.00. A positive electrode active material was obtained in the same manner as in 2.

【0043】

The obtained positive electrode active material was analyzed by powder X-ray diffraction using Cu Kα rays. As a result, in addition to the lithium nickel composite oxide attributed to hexagonal crystals, Li as an oxygen absorber₃VO₄The peak of was confirmed. The lattice constant of the lithium nickel composite oxide calculated from the X-ray diffraction pattern is almost the same as the lattice constant of the lithium nickel composite oxide before the addition of vanadium, and vanadium is dissolved in the lithium nickel composite oxide. It was presumed not. When the composition of the positive electrode active material was analyzed, the molar ratio of vanadium to nickel + cobalt + aluminum was 0.02: 1.00, and considering that vanadium was not solid-dissolved, oxygen to the lithium nickel composite oxide was taken into consideration. Li as an absorbent₃VO₄It can be said that the molar ratio of was 2%.

【0044】

The initial capacitance measurement, differential scanning calorimetry, and TG-MS measurement were performed in the same manner as in Example 1. The measurement results are shown in Table 1, Fig. 2 and Fig. 5.

【0045】

(Example 4) Commercially available lithium hydroxide monohydrate was dissolved in pure water, diindium trioxide was added so that the molar ratio of lithium to indium was 1: 1 and the mixture was stirred. LiNi obtained in the same manner as in Example 1 so that the molar ratio of indium to nickel + cobalt + aluminum was 0.010: 1.00 in this aqueous solution._0.83Co_0.14Al_0.₀₃O₂Was added, heated and stirred, and dried. The obtained dried product has an oxygen flow rate of 3000 cm.³It was fired at 750 ° C. for 20 hours in an air stream of / min and cooled to room temperature to obtain a positive electrode active material composed of an indium-containing lithium-nickel composite oxide.

【0046】

The obtained positive electrode active material was analyzed by powder X-ray diffraction using Cu Kα rays. As a result, in addition to the lithium nickel composite oxide attributed to hexagonal crystals, LiInO as an oxygen absorber₂The peak of was confirmed. The lattice constant of the lithium nickel composite oxide calculated from the X-ray diffraction pattern is almost the same as the lattice constant of the lithium nickel composite oxide before the addition of indium, and indium is dissolved in the lithium nickel composite oxide. It was presumed not. When the composition of the positive electrode active material was analyzed, the molar ratio of indium to nickel + cobalt + aluminum was 0.01: 1.00, and considering that indium was not solid-dissolved, oxygen to the lithium nickel composite oxide was added. LiInO as an absorbent₂It can be said that the molar ratio of was 1%.

【0047】

The initial capacitance measurement, differential scanning calorimetry, and TG-MS measurement were performed in the same manner as in Example 1. The measurement results are shown in Table 1, Fig. 2 and Fig. 6.

【0048】

(Example 5) Commercially available lithium hydroxide monohydrate was dissolved in pure water, diindium trioxide was added so that the molar ratio of lithium to indium was 1: 1 and the mixture was stirred. LiNi obtained in the same manner as in Example 1 so that the molar ratio of indium to nickel + cobalt + aluminum was 0.020: 1.00 in this aqueous solution._0.83Co_0.14Al_0.₀₃O₂Was added, heated and stirred, and dried. The obtained dried product has an oxygen flow rate of 3000 cm.³It was fired at 750 ° C. for 20 hours in an air stream of / min and cooled to room temperature to obtain a positive electrode active material composed of an indium-containing lithium-nickel composite oxide.

【0049】

The obtained positive electrode active material was analyzed by powder X-ray diffraction using Cu Kα rays. As a result, in addition to the lithium nickel composite oxide attributed to hexagonal crystals, LiInO as an oxygen absorber₂The peak of was confirmed. The lattice constant of the lithium nickel composite oxide calculated from the X-ray diffraction pattern is almost the same as the lattice constant of the lithium nickel composite oxide before the addition of indium, and indium is dissolved in the lithium nickel composite oxide. It was presumed not. When the composition of the positive electrode active material was analyzed, the molar ratio of indium to nickel + cobalt + aluminum was 0.02: 1.00, and considering that indium was not solid-dissolved, oxygen to the lithium nickel composite oxide was added. LiInO as an absorbent₂It can be said that the molar ratio of was 2%.

【0050】

The initial capacitance measurement, differential scanning calorimetry, and TG-MS measurement were performed in the same manner as in Example 1. The measurement results are shown in Table 1, Fig. 2 and Fig. 7.

【0051】

(Comparative Example 1) Commercially available lithium hydroxide monohydrate and a composite hydroxide in which nickel, cobalt, and aluminum are solid-dissolved at a molar ratio of 83: 14: 3 are mixed with lithium, nickel, cobalt, and aluminum. Weighed so that the molar ratio of each was 1.03: 1.00, and mixed well. This mixed powder has an oxygen flow rate of 3000 cm.³After calcining at 350 ° C for 2 hours in an air stream of / min, it was calcined at 750 ° C for 20 hours and cooled to room temperature to obtain a positive electrode active material composed of a lithium nickel composite oxide.

【0052】

When the obtained positive electrode active material was analyzed by powder X-ray diffraction using Cu Kα rays, only the lithium nickel composite oxide attributed to hexagonal crystals could be confirmed.

【0053】

When the composition of the positive electrode active material was analyzed, the molar ratio of lithium to nickel + cobalt + aluminum was 1.03: 1.00.

【0054】

The initial capacitance measurement, differential scanning calorimetry, and TG-MS measurement were performed in the same manner as in Example 1. The measurement results are shown in Table 1, Fig. 2 and Fig. 8.

【0055】

(Comparative Example 2) Except that the molar ratio of vanadium to nickel + cobalt + aluminum was 0.04: 1.00, and the molar ratio of lithium to nickel + cobalt + aluminum was 1.150: 1.000. A positive electrode active material was obtained in the same manner as in Example 2.

【0056】

The obtained positive electrode active material was analyzed by powder X-ray diffraction using Cu Kα rays. As a result, in addition to the lithium nickel composite oxide attributed to hexagonal crystals, Li as an oxygen absorber₃VO₄The peak of was confirmed. The lattice constant of the lithium nickel composite oxide calculated from the X-ray diffraction pattern is almost the same as the lattice constant of the lithium nickel composite oxide before the addition of vanadium, and vanadium is dissolved in the lithium nickel composite oxide. It was presumed not. When the composition of the positive electrode active material was analyzed, the molar ratio of vanadium to nickel + cobalt + aluminum was 0.04: 1.00, and considering that vanadium was not solid-dissolved, oxygen to the lithium nickel composite oxide was taken into consideration. Li as an absorbent₃VO₄It can be said that the molar ratio of was 4%.

【0057】

The initial capacity was measured in the same manner as in Example 1. The measurement results are shown in Table 1.

【0058】

[table 1]

<img file="JP2003123749A_D0001.tif" />【0059】

From Table 1, the initial capacities of the batteries of Examples 1 to 5 are slightly smaller than the initial capacities of the batteries of Comparative Examples 1 and 2 depending on the amount of the oxygen absorbing compound added. When an oxygen absorbing compound of 2 at% or less is added, the decrease in the initial volume can be suppressed to the extent that there is no problem in practical use.

【0060】

Further, by the differential scanning calorimetry shown in FIG. 2, the positive electrode materials of Examples 1 to 5 alleviate the rapid heat generation as seen in the positive electrode materials of Comparative Example 1, and the reaction is relatively mild. It can be seen that all of them have a great effect on improving the thermal stability.

【0061】

Looking at the TG-MS measurement results in FIGS. 3 to 7, the oxygen released when the positive electrode material is decomposed is usually not seen because this oxygen reacts (combusts) with the electrolytic solution and changes to carbon dioxide. Because it is. Looking at the behavior of carbon dioxide at 250 ° C or higher corresponding to the decomposition of the positive electrode active material, in the positive electrode material of Comparative Example 1 shown in FIG. 8, carbon dioxide is released due to the reaction of the electrolytic solution. No carbon dioxide emission is observed in the positive electrode materials of Examples 1 to 5 shown in FIGS. 3 to 7. It is considered that this is because the oxygen released from the positive electrode active material is absorbed by the oxygen absorbing compound, the reaction with the electrolytic solution is suppressed, and as a result, the generation of carbon dioxide is suppressed. As described above, it can be seen that the coexistence of the oxygen-absorbing compound in the positive electrode material relaxes the combustion reaction of the electrolytic solution and is effective in improving the thermal stability.

【0062】

[Effect of the invention]

A battery using the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has improved thermal stability with almost no loss of high initial capacity.

[Simple explanation of drawings]

[Figure 1]

It is a partially broken perspective view which shows the 2032 type coin battery.

[Figure 2]

It is a graph which shows the measurement result of the differential scanning calorimetry in Examples 1 to 5 and Comparative Example 1.

[Fig. 3]

It is a graph which shows the measurement result of the TG-MS measurement in Example 1.

[Fig. 4]

It is a graph which shows the measurement result of the TG-MS measurement in Example 2.

[Fig. 5]

It is a graph which shows the measurement result of the TG-MS measurement in Example 3.

[Fig. 6]

It is a graph which shows the measurement result of the TG-MS measurement in Example 4.

[Fig. 7]

It is a graph which shows the measurement result of the TG-MS measurement in Example 5.

[Fig. 8]

It is a graph which shows the measurement result of the TG-MS measurement in the comparative example 1.

[Explanation of symbols]

1 Lithium metal negative electrode 2 Separator (impregnated with electrolyte) 3 Positive electrode (evaluation electrode) 4 Gasket 5 Negative electrode can 6 Positive electrode can