JP6986879B2 - Positive electrode active material particle powder for non-aqueous electrolyte secondary battery and its manufacturing method, and non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery.

In recent years, electronic devices such as AV devices and personal computers have been rapidly made portable and cordless, and there is an increasing demand for a secondary battery that is compact, lightweight, and has a high energy density as a power source for driving these devices. Under such circumstances, a lithium ion secondary battery having advantages of high charge / discharge voltage and large charge / discharge capacity is attracting attention.

Conventionally, positive electrode active materials useful for high-energy lithium-ion secondary batteries having a 4V class voltage include those having a spinel-type structure such as _{LiMn 2} O _{4 , LiMnO 2} , LiCoO ₂ , and LiCo _1-x Ni. those of the layered-type structure, such as _x O _2, LiNiO ₂ is generally known. In recent years, in addition to _{these, Li 1 + s Ni x Co} y Mn z M t O 2 (M = Mg, Al , _{etc.), Li x Ni 1-y} -z Co y M z O 2 (M = Mn , etc.) Such as, positive electrode active material particles containing at least Ni, Co and Mn and having a layered rock salt structure have also been proposed (Patent Documents 1 and 2).

In the positive electrode of the lithium ion secondary battery using the positive electrode active material particle powder having the layered rock salt structure, lithium ions are desorbed during charging and lithium ions are inserted during discharging. Due to repeated desorption and insertion of lithium ions during such charging and discharging, the crystal strain of the positive electrode active material particles having a layered rock salt structure becomes large, the grain boundaries are cracked, and the characteristics are deteriorated.

Japanese Unexamined Patent Publication No. 2015-026454 Japanese Unexamined Patent Publication No. 2015-0563668

As described above, the lithium ion secondary battery including the positive electrode active material particles having a large crystal strain tends to have a decrease in charge / discharge efficiency and an increase in resistance. Therefore, it is desired to develop a positive electrode active material particle powder capable of providing a lithium ion secondary battery which exhibits a charge / discharge efficiency that is practically satisfactory and suppresses an increase in resistance.

The present invention has been made in view of the above problems, and an object thereof is a positive electrode active material particle powder for a non-aqueous electrolyte secondary battery capable of improving charge / discharge efficiency and resistance. It is an object of the present invention to provide a method for easily producing a positive electrode active material particle powder. Further, an object of the present invention is to provide a non-aqueous electrolyte secondary battery using such a positive electrode active material particle powder as a positive electrode.

In order to achieve the above object, in the present invention, a positive electrode active material particle powder using a lithium composite oxide containing at least one of Li, Ni, Co, Mn and Al, and optionally Mg is used. It was composed of the rate of change in the water content in a specific range.

Specifically, the positive electrode active material particle powder according to the present invention has a layered rock salt structure, and at least one selected from Li, Ni, Co, Mn, Al, and Mg (however, Mn and Al). It uses a lithium composite oxide containing (including at least one).
The rate of change (without unit) of the water content represented by the following formula (1) is 0.3 or more and 9.5 or less.
Rate of change in water content = | (W _2- W ₁ ) / W ₁ | ... (1)
here,
W ₁ : Moisture content of lithium composite oxide (ppm)
W ₂ : Moisture content (ppm) of positive electrode active material particle powder
Is.

Further, the positive electrode active material particle powder according to the present invention preferably has a reduction rate (without unit) of crystal strain represented by the following formula (2) of −0.25 or more and less than 0.
Decrease rate of crystal strain = (S _2- S ₁ ) / S ₁ ... (2)
here,
S ₁ : Crystal strain (%) of lithium composite oxide
S ₂ : Crystal strain (%) of positive electrode active material particle powder
Is.

The positive electrode active material particle powder according to the present invention having such a configuration can be used for the positive electrode of a non-aqueous electrolyte secondary battery, and can improve the charge / discharge efficiency and resistance of the non-aqueous electrolyte secondary battery. can.

Further, the positive electrode active material particle powder according to the present invention includes P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, in addition to the above Ni, Co, Mn, Al, and Mg. It preferably contains at least one metal selected from Nb and W.

In the positive electrode active material particle powder according to the present invention, at least one metal selected from the P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W is the above-mentioned metal. It may be substituted with a part of at least one selected from Ni, Co, Mn, Al, and Mg, and may be coated on the surface and grain boundaries of the aggregated secondary particles of the lithium composite oxide. ..

In order to achieve the above object, in the present invention, a method for producing a positive electrode active material particle powder is a lithium composite oxide containing Li, Ni, Co, at least one of Mn and Al, and optionally Mg. In addition, it was composed of steps of performing a moisture exposure treatment in an atmosphere in a specific relative humidity range.

Specifically, the production method according to the present invention has a layered rock salt structure, and at least one selected from Li, Ni, Co, Mn, Al and Mg (provided that at least one of Mn and Al is used). A method for producing the positive electrode active material particle powder using a lithium composite oxide containing (including).
A composite compound precursor was prepared using a nickel compound, a cobalt compound, and at least one compound selected from a manganese compound, an aluminum compound, and a magnesium compound (provided that the compound contains at least one of the manganese compound and the aluminum compound). After that, a mixture obtained by mixing a lithium compound and at least one compound optionally selected from a manganese compound, an aluminum compound and a magnesium compound with the composite compound precursor was fired to obtain Li and Ni. , The first step of preparing a lithium compound oxide containing Co and at least one selected from Mn, Al and Mg (provided that it contains at least one of Mn and Al).
The lithium composite oxide is characterized by including at least a second step of subjecting the lithium composite oxide to a moisture exposure treatment in an atmosphere having a relative humidity of 30% or more and 80% or less.

By the production method according to the present invention having such a configuration, a positive electrode active material particle powder capable of improving the charge / discharge efficiency and the resistance by using a non-aqueous electrolyte secondary battery can be easily produced. Can be done.

In the production method according to the present invention, it is preferable that the lithium composite oxide subjected to the moisture exposure treatment is further provided with a third step of heat-treating the lithium composite oxide. Further, the heat treatment is preferably performed at 180 ° C. or higher and 400 ° C. or lower.

When the positive electrode active material particle powder obtained by such a production method is used for the positive electrode of the non-aqueous electrolyte secondary battery, the discharge capacity of the non-aqueous electrolyte secondary battery can be improved. Moreover, it is possible to reduce the water content of the positive electrode active material particle powder while maintaining each characteristic after the water exposure treatment and maintaining the cycle characteristic in an improved state. Further, when the positive electrode of the non-aqueous electrolyte secondary battery is manufactured, the slurry containing the positive electrode active material particle powder is unlikely to gel.

Further, in the production method according to the present invention, a compound of at least one metal selected from P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W is further used. The complex compound precursor may be prepared, and the complex compound precursor may be further selected from P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W. At least one metal compound may be mixed.

Further, the non-aqueous electrolyte secondary battery of the present invention specifically has a layered rock salt structure, and at least one selected from Li, Ni, Co, Mn, Al and Mg (provided that Mn and Mn and Mg). The positive electrode active material particle powder using a lithium composite oxide containing (including at least one of Al) is used for the positive electrode.

Such a non-aqueous electrolyte secondary battery has improved charge / discharge efficiency and improved resistance.

The positive electrode active material particle powder according to the present invention can improve the charge / discharge efficiency of the non-aqueous electrolyte secondary battery and improve the resistance. Further, by the production method according to the present invention, such a positive electrode active material particle powder can be easily produced.

It is a graph which shows the XRD diffraction of the positive electrode active material particle powder which concerns on Example 2. FIG. It is a Core-Cole plot which shows the measurement result of the impedance of the symmetric cell by the positive electrode of the non-aqueous electrolyte secondary battery which concerns on Example 1 and Reference Example 1.

Hereinafter, embodiments for carrying out the present invention will be described. The following description of preferred embodiments is merely exemplary and is not intended to limit the invention, its application methods or its uses.

[Manufacturing method of positive electrode active material particle powder]
A method for producing a positive electrode active material particle powder according to an embodiment of the present invention will be described. The positive electrode active material particle powder produced by the present invention is used for the positive electrode of a non-aqueous electrolyte secondary battery.

The positive electrode active material particle powder produced by the production method according to the present embodiment has a layered rock salt structure, and at least one selected from Li, Ni, Co, Mn, Al, and Mg (however, Mn). And a lithium composite oxide containing at least one of Al). Such a method for producing positive electrode active material particle powder includes at least the following first step and second step.

<First step>
In the first step, a composite compound is used using a nickel compound, a cobalt compound, and at least one compound selected from a manganese compound, an aluminum compound, and a magnesium compound (provided to include at least one of the manganese compound and the aluminum compound). After preparing the precursor, the composite compound precursor was mixed with a lithium compound and at least one compound optionally selected from a manganese compound, an aluminum compound and a magnesium compound, and the mixture was fired. A lithium composite oxide containing Li, Ni, Co, and at least one selected from Mn, Al, and Mg (provided that it contains at least one of Mn and Al) is prepared.

The nickel compound used for preparing the composite compound precursor is not particularly limited, and is, for example, nickel sulfate, nickel oxide, nickel hydroxide, nickel nitrate, nickel carbonate, nickel chloride, nickel iodide, metallic nickel and the like. Can be mentioned. Among these, nickel sulfate is preferable because the coprecipitation reaction by the wet step described later can be easily performed.

The cobalt compound is not particularly limited, and examples thereof include cobalt sulfate, cobalt oxide, cobalt hydroxide, cobalt nitrate, cobalt carbonate, cobalt chloride, cobalt iodide, and metallic cobalt. Among these, cobalt sulfate is preferable because the coprecipitation reaction by the wet step described later can be easily performed.

The manganese compound is not particularly limited, and examples thereof include manganese sulfate, manganese oxide, manganese hydroxide, manganese nitrate, manganese carbonate, manganese chloride, manganese iodide, and metallic manganese. Among these, manganese sulfate is preferable when it is used for the coprecipitation reaction by the wet step described later, because the coprecipitation reaction can be easily performed. Further, when used in the dry process described later, manganese oxide is preferable.

The aluminum compound is not particularly limited, and examples thereof include sodium aluminate, aluminum sulfate, aluminum oxide, aluminum hydroxide, aluminum nitrate, aluminum carbonate, aluminum chloride, aluminum iodide, and metallic aluminum. Among these, when used for the coprecipitation reaction by the wet step described later, sodium aluminate is preferable because the coprecipitation reaction can be easily performed. Further, when used in the dry process described later, aluminum hydroxide is preferable.

The magnesium compound is not particularly limited, and examples thereof include magnesium sulfate, magnesium oxide, magnesium hydroxide, magnesium nitrate, magnesium carbonate, magnesium chloride, magnesium iodide, and metallic magnesium. Among these, magnesium sulfate is preferable when it is used for the coprecipitation reaction by the wet step described later, because the coprecipitation reaction can be easily performed. Further, when used in the dry process described later, magnesium oxide is preferable.

The compound compound precursor can be prepared, for example, by subjecting each compound to a wet coprecipitation reaction. Specifically, the ratio of the nickel compound, the cobalt compound, and at least one compound selected from the manganese compound, the aluminum compound, and the magnesium compound (however, including at least one of the manganese compound and the aluminum compound) is set. The elements (Ni, Co, and at least one of Mn, Al, and Mg (Mn and / or Al are essential)) are adjusted to the desired ratio, and these compounds are dissolved in water and / or an organic solvent. Let me. Then, an appropriate amount of a precipitant is added to the solution of these compounds, and the mixture is stirred and mixed, and these compounds are co-precipitated and overflowed to obtain a reaction product, which is then washed with water and dried to obtain a composite compound precursor. Is obtained.

The concentration of the nickel compound, the cobalt compound, and at least one compound selected from the manganese compound, the aluminum compound, and the magnesium compound (however, including at least one of the manganese compound and the aluminum compound) in the solution is particularly limited. Although not, it is preferably about 1 mol / L to about 2 mol / L. Further, as the precipitating agent, for example, a mixture of a caustic soda solution and an ammonia solution can be preferably used. The concentration of the caustic soda solution and the concentration of the ammonia solution are not particularly limited, but the concentration of the caustic soda solution is preferably about 5.0 mol / L to about 8.0 mol / L, and the concentration of the ammonia solution is , It is preferably about 5.0 mol / L to about 8.0 mol / L.

The conditions for the coprecipitation reaction are appropriately set so that the residual S content is about 0.2 wt% or less, the Na content is about 300 ppm or less, and the total amount of impurities including water is about 0.4 wt% or less in the composite compound precursor. It is more preferable to set it. If the amount of impurities in the composite compound precursor is large, it becomes difficult to prepare a lithium composite oxide from the mixture obtained by mixing with the lithium compound, and the obtained positive electrode active material particle powder is used to make a non-aqueous electrolyte secondary battery. When manufactured, there is a risk of reduced stability.

When a manganese compound is used, it is preferable that the reactant obtained by overflowing after the coprecipitation reaction is dried to such an extent that _{NiMnO 3 is not generated.} As a result of such drying, when a lithium composite oxide is prepared from a mixture obtained by mixing with a lithium compound, the reaction easily proceeds sufficiently, and a highly stable positive electrode active material particle powder can be obtained.

Then, the composite compound precursor obtained as described above, a lithium compound, and at least one compound optionally selected from a manganese compound, an aluminum compound, and a magnesium compound are mixed at a desired ratio to obtain a uniform mixture. To get. At least one compound selected from any of these arbitrary manganese compounds, aluminum compounds and magnesium compounds can be mixed with the composite compound precursor and the lithium compound in a dry step.

The lithium compound is not particularly limited, and is, for example, lithium carbonate, lithium hydroxide / monohydrate, anhydrous lithium hydroxide, lithium nitrate, lithium acetate, lithium bromide, lithium chloride, lithium citrate, and fluoride. Examples thereof include lithium, lithium iodide, lithium lactic acid, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, lithium oxide and the like. Among these, lithium carbonate, lithium hydroxide / monohydrate, from the viewpoint that the reaction can be easily proceeded when a lithium composite oxide is prepared from a mixture obtained by mixing with the composite compound precursor. , And anhydrous lithium hydroxide are preferred.

The desired ratio of the composite compound precursor, the lithium compound, and at least one compound selected from any manganese compound, aluminum compound, and magnesium compound is the basic composition (composition) of the lithium composite oxide described later. Formula: The ratio is such that it has _{Li a} (Ni _p Co _q Mn _r Al _1-p-q-r Mg _u ) O _2). The molar ratio of Li to the sum of Ni, Co, (Mn and / or Al), and any Mg [Li / (Ni + Co + (Mn and / or Al) + any Mg)], that is, a in the formula. Specific examples of the range will be described later.

The obtained mixture was fired in an oxidizing atmosphere with appropriately adjusted conditions to obtain at least one selected from Li, Ni, Co, Mn, Al and Mg (however, at least one of Mn and Al). Includes) and to prepare a lithium composite oxide containing.

The heating temperature at the time of firing is not particularly limited, but is preferably, for example, about 700 ° C to about 1000 ° C. When firing at a heating temperature in this range, Li, Ni, Co, Mn and / or Al, and arbitrary Mg tend to be uniform, and there is no risk of increasing oxygen defects. The holding time at the time of firing is not particularly limited, but is preferably, for example, about 3 hours to about 7 hours.

The water content of the lithium composite oxide obtained in such a first step is usually about 80 ppm to about 220 ppm.

<Second step>
In the second step, the lithium composite oxide obtained in the first step is subjected to a moisture exposure treatment in an atmosphere having a relative humidity of 30% or more and 80% or less.

Battery materials generally used for positive electrodes and negative electrodes usually contain components (elements) that are adversely affected by moisture. Therefore, for example, the water exposure treatment to the lithium composite oxide constituting the positive electrode active material particle powder has not been performed conventionally because there is a concern that the quality of the positive electrode active material particle powder may be significantly deteriorated.

On the other hand, in the production method according to the present embodiment, it is largely provided that the second step of subjecting the lithium composite oxide obtained in the first step to the moisture exposure treatment in an atmosphere of a specific range of relative humidity is provided. It is one of the features.

When the lithium composite oxide is subjected to a moisture exposure treatment, the relative humidity is adjusted to 30% or more and 80% or less, preferably 30% or more and 70% or less. By adjusting the relative humidity to 30% or more, the lithium composite oxide is sufficiently exposed to water, and when the obtained positive electrode active material particle powder is used for the positive electrode of the non-aqueous electrolyte secondary battery, the non-aqueous electrolyte is used. The effect of increasing the discharge capacity of the secondary battery, improving the charge / discharge efficiency, and the effect of improving the resistance are fully exhibited. Further, by adjusting the relative humidity to 80% or less, the water content of the obtained positive electrode active material particle powder did not become too large, and the positive electrode active material particle powder was used for the positive electrode of the non-aqueous electrolyte secondary battery. At that time, the deterioration of the cycle characteristics of the non-aqueous electrolyte secondary battery can be suppressed to a small extent, and when the positive electrode of the non-aqueous electrolyte secondary battery is produced, the slurry containing the positive electrode active material particle powder is gelled. There is no.

The temperature at which the moisture exposure treatment is applied is not particularly limited, but is preferably adjusted to, for example, about 20 ° C to about 30 ° C. The time for performing the water exposure treatment is not particularly limited, but in addition to setting the relative humidity, for example, the water content of the obtained positive electrode active material particle powder is set to a suitable range described later. It is preferably 1 minute to about 30 minutes.

For the moisture exposure treatment, for example, a normal constant temperature and humidity chamber can be used. The constant temperature and humidity chamber is set to a predetermined relative humidity in the above range and, for example, a predetermined temperature in the above range, and the lithium composite oxide powder obtained in the first step is used, for example, for a predetermined time in the above range. By placing the lithium composite oxide in the constant temperature and humidity chamber, the lithium composite oxide is subjected to a moisture exposure treatment.

Thus, a first step and are prepared via the second step, the lithium composite oxide after moisture exposure process as a cathode active material particles of the manufacturing method according to the present embodiment, for example, the composition formula: Li _a having a basic composition represented by _{(Ni p Co q Mn r Al} 1-p-q-r Mg u) O 2.

In the composition formula, a indicates the amount (mol) of Li in 1 mol of (Ni + Co + (Mn and / or Al) + arbitrary Mg) in the lithium composite oxide prepared in the first step. The range of a is preferably 0.96 ≦ a ≦ 1.15, and more preferably 0.98 ≦ a ≦ 1.10.

In the composition formula, p indicates the amount (mol) of Ni in the lithium composite oxide prepared in the first step. The range of p is preferably 0 <p ≦ 0.97, more preferably 0.20 ≦ p ≦ 0.97.

In the composition formula, q indicates the amount (mol) of Co in the lithium composite oxide prepared in the first step. The range of q is preferably 0 <q ≦ 0.50, more preferably 0.03 ≦ q ≦ 0.40.

In the composition formula, p and q satisfy p + q <1.00.

When the target positive electrode active material particle powder contains Mn, in the composition formula, r indicates the amount (mol) of Mn in the lithium composite oxide prepared in the first step. The range of r is preferably 0 <r ≦ 0.50, more preferably 0 <r ≦ 0.40, and more preferably p + q + r ≦ 1.00.

When the target positive electrode active material particle powder contains Al, the amount (mol) of Al in the lithium composite oxide prepared in the first step is represented by (1-p-q-r). The range of (1-p-q-r) is preferably 0 <(1-p-q-r) ≤ 0.20, and 0 <(1-p-q-r) ≤ 0.10. It is more preferable to have.

When the target positive electrode active material particle powder further contains Mg, the amount (mol) of Mg in the lithium composite oxide prepared in the first step is represented by u. The range of u is preferably 0 <u ≦ 0.20, more preferably 0 <u ≦ 0.15.

Incidentally, the lithium composite oxide has a layered rock salt structure, e.g., unlike LiMn ₂ O ₄ spinel oxide, a solid solution region of Li is extremely small. Therefore, in the crystal immediately after the preparation of the lithium composite oxide, the ratio of Li to Ni, Co, Mn and / or Al, and any Mg [Li / (Ni + Co + (Mn and / or Al) + optional). Mg) = a] does not deviate significantly from 1.00 as described above. Further, in the present embodiment, since the positive electrode active material particle powder is formed by aggregated secondary particles which are aggregates of primary particles, grain boundaries exist in the particles.

Further, the positive electrode active material particle powder according to the present embodiment is, for example, P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, in addition to Ni, Co, Mn, Al, and Mg. , Nb, and W can contain at least one metal selected from. The content form thereof is not particularly limited, and may be substituted with a part of at least one selected from Ni, Co, Mn, Al, and Mg in the crystal lattice and may be present in the lithium composite oxide. It may be present covered with the surface of the aggregated secondary particles and the grain boundaries.

In order to include at least one metal selected from P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W in the positive electrode active material particle powder, The compound of these metals may be used to prepare a composite compound precursor in the wet step, or the compound of these metals may be mixed with the composite compound precursor in the dry step.

By the water exposure treatment in the second step, the water content of the target positive electrode active material particle powder is preferably adjusted to 300 ppm or more and 1200 ppm or less, and more preferably 400 ppm or more and 1100 ppm or less. When the water content of the positive electrode active material particle powder obtained after the water exposure treatment is 300 ppm or more, the non-aqueous electrolyte secondary battery is used when the positive electrode active material particle powder is used as the positive electrode of the non-aqueous electrolyte secondary battery. The effect of increasing the discharge capacity of the battery and improving the charge / discharge efficiency is more fully exhibited. When the water content is 1200 ppm or less, when the positive electrode active material particle powder is used for the positive electrode of the non-aqueous electrolyte secondary battery, the deterioration of the cycle characteristics of the non-aqueous electrolyte secondary battery can be suppressed to a small extent. When the positive electrode of the non-aqueous electrolyte secondary battery is manufactured, the slurry containing the positive electrode active material particle powder does not gel.

Compared with the positive electrode active material particle powder having the same composition and not subjected to the water exposure treatment, the positive electrode active material particle powder obtained after the water exposure treatment has a reduction in crystal strain of about 0.02% to 0.06% (numerical value). ) Is observed.

When the positive electrode active material particle powder obtained after the water exposure treatment is used for the positive electrode of the non-aqueous electrolyte secondary battery, the discharge capacity of the non-aqueous electrolyte secondary battery is the composition of the positive electrode active material particle powder, the water content, and the crystal strain. However, for example, when Li _1.04 (Ni _0.5 Co _0.2 Mn _0.3 ) O ₂ is used, a positive electrode active material particle powder having the same composition and not subjected to moisture exposure treatment is used. Compared with the case where it is used for the positive electrode of the non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery using the positive electrode active material particle powder obtained after the water exposure treatment for the positive electrode has about 1 mAh / g to about 5 mAh / g. An increase in the discharge capacity (increase in the numerical value) is observed.

Similarly, when the positive electrode active material particle powder obtained after the water exposure treatment is used for the positive electrode of the non-aqueous electrolyte secondary battery, the charge / discharge efficiency of the non-aqueous electrolyte secondary battery is the composition and content of the positive electrode active material particle powder. Although it depends on the amount of water, crystal strain, etc., it is obtained after the water exposure treatment as compared with the case where the positive electrode active material particle powder having the same composition and not subjected to the water exposure treatment is used for the positive electrode of the non-aqueous electrolyte secondary battery. In the non-aqueous electrolyte secondary battery using the positive electrode active material particle powder as the positive electrode, an improvement in charge / discharge efficiency (increase in numerical value) of about 1% to 2.5% is observed.

<Third step>
As described above, the lithium composite oxide which has been subjected to the moisture exposure treatment to be the positive electrode active material particle powder can be prepared through the first step and the second step of the production method according to the present embodiment. The production method according to the embodiment preferably further comprises a third step of heat-treating the water-exposed lithium composite oxide to dry the water from the positive electrode active material particle powder.

When the positive electrode active material particle powder obtained by further heat-treating the lithium composite oxide subjected to the water exposure treatment is used for the positive electrode of the non-aqueous electrolyte secondary battery, the cycle characteristics of the non-aqueous electrolyte secondary battery, In particular, the high temperature cycle characteristics can be improved as compared with the case where the positive electrode active material particle powder before the heat treatment is used. Moreover, the water content of the positive electrode active material particle powder should be reduced while maintaining each characteristic, including the effect (obtained characteristics) developed by subjecting the lithium composite oxide to water exposure treatment. Therefore, it is more suitable as a positive electrode for a non-aqueous electrolyte secondary battery.

When the lithium composite oxide subjected to the moisture exposure treatment is heat-treated, the heating temperature is preferably adjusted to 180 ° C. or higher and 400 ° C. or lower, more preferably 200 ° C. or higher and 350 ° C. or lower. By adjusting the heating temperature to 180 ° C. or higher, the effect of improving the cycle characteristics, particularly the high temperature cycle characteristics, and the effect of preventing the gelation are sufficiently exhibited. Further, by adjusting the heating temperature to 400 ° C. or lower, the water content of the positive electrode active material particle powder can be sufficiently reduced, and the discharge capacity and charge / discharge efficiency of the non-aqueous electrolyte secondary battery are more preferable. Maintained in a state.

The time for heat treatment is not particularly limited, but is, for example, about 1 hour or more so that the water content of the obtained positive electrode active material particle powder is within a suitable range described later in combination with the setting of the heating temperature. It is preferably about 6 hours. However, for a lithium composite oxide having a Ni content of more than 60 mol%, it is preferable to carry out the operation in an oxygen atmosphere or a decarboxylation atmosphere.

Further, the heat treatment for the lithium composite oxide subjected to the moisture exposure treatment is performed, for example, by exposing the lithium composite oxide to an atmosphere of about 20 ° C. and a relative humidity of about 30 to 40%, and then in an air atmosphere. Just do it. However, for lithium composite oxides having a Ni content of more than 60 mol%, it is preferable to carry out heat treatment in an oxygen atmosphere or a decarboxylation atmosphere.

For the heat treatment, for example, a normal firing furnace can be used. The firing furnace is set to, for example, a predetermined heating temperature in the above range, and the lithium composite oxide obtained in the second step after the moisture exposure treatment is placed in the firing furnace, for example, for a predetermined time in the above range. By doing so, the lithium composite oxide after the water exposure treatment is heat-treated.

As described above, the water content of the positive electrode active material particle powder prepared through the first step, the second step, and the third step of the production method according to the present embodiment is adjusted to 100 ppm or less. It is more preferable that the amount is adjusted to 90 ppm or less. When the water content of the positive electrode active material particle powder obtained after the heat treatment is 100 ppm or less, the cycle of the non-aqueous electrolyte secondary battery when the positive electrode active material particle powder is used for the positive electrode of the non-aqueous electrolyte secondary battery The effect of improving the characteristics, particularly the high temperature cycle characteristics, and the effect of preventing gelation of the slurry are more sufficiently exhibited.

The crystal strain of the positive electrode active material particle powder obtained after the heat treatment varies depending on the composition of the positive electrode active material particle powder, the water content, etc., but for example, the above Li _1.04 (Ni _0.5 Co _0.2 Mn _{0) .3} ) When O ₂ is used, it is about 0.40% or more and about 0.46% or less. Therefore, the crystal strain of the positive electrode active material particle powder obtained after the heat treatment is smaller than the crystal strain of 0.471% of the positive electrode active material particle powder having the same composition and not subjected to the water exposure treatment and the heat treatment. Is recognized.

When the positive electrode active material particle powder obtained after the heat treatment is used for the positive electrode of the non-aqueous electrolyte secondary battery, the discharge capacity of the non-aqueous electrolyte secondary battery is determined by the composition of the positive electrode active material particle powder, the water content, crystal strain, etc. However, for example, when the above Li _1.04 (Ni _0.5 Co _0.2 Mn _0.3 ) O ₂ is used, it is about 167 mAh / g or more and about 172 mAh / g or less. Therefore, for the discharge capacity of the non-aqueous electrolyte secondary battery using the positive electrode active material particle powder obtained after the heat treatment for the positive electrode, the positive electrode active material particle powder having the same composition but not subjected to the water exposure treatment and the heat treatment is used for the positive electrode. When compared with the discharge capacity of the non-aqueous electrolyte secondary battery of 166.9 mAh / g, it is recognized that the capacity is about the same or higher.

Similarly, when the positive electrode active material particle powder obtained after the heat treatment is used for the positive electrode of the non-aqueous electrolyte secondary battery, the charge / discharge efficiency of the non-aqueous electrolyte secondary battery is the composition and the content of water content of the positive electrode active material particle powder. However, for example, when the above-mentioned Li _1.04 (Ni _0.5 Co _0.2 Mn _0.3 ) O ₂ is used, it is about 87% or more and about 92% or less. Therefore, the charge / discharge efficiency of the non-aqueous electrolyte secondary battery using the positive electrode active material particle powder obtained after the heat treatment as the positive electrode is such that the positive electrode active material particle powder having the same composition but not subjected to the water exposure treatment and the heat treatment is used as the positive electrode. When compared with the charge / discharge efficiency of 87.3% of the non-aqueous electrolyte secondary battery used, it is recognized that the efficiency is about the same or higher.

Similarly, when the positive electrode active material particle powder obtained after the heat treatment is used for the positive electrode of the non-aqueous electrolyte secondary battery, the high temperature cycle characteristics of the non-aqueous electrolyte secondary battery are the composition and the water content of the positive electrode active material particle powder. Although it depends on the crystal strain and the like, for example, when the above Li _1.04 (Ni _0.5 Co _0.2 Mn _0.3 ) O ₂ is used, it is about 90% or more and about 92% or less. Therefore, the high temperature cycle characteristics of the non-aqueous electrolyte secondary battery using the positive electrode active material particle powder obtained after the heat treatment for the positive electrode are such that the positive electrode active material particle powder having the same composition but not subjected to the water exposure treatment and the heat treatment is used as the positive electrode. When compared with 90.7%, which is the high temperature cycle characteristic of the non-aqueous electrolyte secondary battery used, it is found to be about the same. Further, in comparison with a non-aqueous electrolyte secondary battery having the same composition and using a positive electrode active material particle powder which has been subjected to moisture exposure treatment and has not been heat-treated as a positive electrode, a positive electrode active material particle powder obtained after heat treatment can be obtained. In the non-aqueous electrolyte secondary battery used for the positive electrode, improvement in high temperature cycle characteristics (increase in numerical value) of about 0.5% to 1.0% is observed.

The method for measuring the water content, the crystal strain, and the discharge capacity, and the method for calculating the charge / discharge efficiency and the high temperature cycle characteristics will be described in detail later in [Example].

[Positive electrode active material particle powder]
The positive electrode active material particle powder according to the present embodiment has a layered rock salt structure, and at least one selected from Li, Ni, Co, Mn, Al, and Mg (however, at least one of Mn and Al). It is a product using a lithium composite oxide containing (including) and can be obtained by the production method according to the present embodiment. Positive electrode active material particles, for example, the composition _formula: has a basic composition represented by _{Li a (Ni p Co q Mn} r Al 1-p-q-r Mg u) O 2. The positive electrode active material particle powder has a water content, crystal strain, and the like as described in the above [Method for producing positive electrode active material particle powder], and is used for the positive electrode of a non-aqueous electrolyte secondary battery. At the same time, it improves the characteristics such as the discharge capacity, charge / discharge efficiency, and high temperature cycle characteristics of the non-aqueous electrolyte secondary battery, and has the following characteristics.

That is, the positive electrode active material particle powder according to the present embodiment is characterized in that the rate of change (without unit) of the water content represented by the following formula (1) is 0.3 or more and 9.5 or less. do.
Rate of change in water content = | (W _2- W ₁ ) / W ₁ | ... (1)
here,
W ₁ : Moisture content of lithium composite oxide (ppm)
W ₂ : Moisture content (ppm) of positive electrode active material particle powder
Is.

Water content W ₁ of the lithium composite oxide, a lithium composite oxide obtained through the first step in the manufacturing method according to this embodiment, i.e., in the water content of the lithium composite oxide before water exposure process be. _{On the other hand, the water content W 2} of the positive electrode active material particle powder is the water content of the positive electrode active material particle powder obtained through the second step, that is, the water content of the lithium composite oxide after the water exposure treatment, or further. It is the water content of the positive electrode active material particle powder obtained through three steps, that is, the lithium composite oxide after the heat treatment.

By the water exposure treatment, the water content of the lithium composite oxide is greatly increased as compared with that before the water exposure treatment, and when the obtained positive electrode active material particle powder is used for the positive electrode of the non-aqueous electrolyte secondary battery, it is not. The effect of increasing the discharge capacity of the water electrolyte secondary battery and improving the charge / discharge efficiency is fully exhibited. On the other hand, when the heat treatment is further performed, the water content of the lithium composite oxide is not only reduced as compared with that before the heat treatment, but also as compared with that before the water exposure treatment. When the positive electrode active material particle powder is used for the positive electrode of the non-aqueous electrolyte secondary battery, the effect of improving the cycle characteristics of the non-aqueous electrolyte secondary battery, especially the high temperature cycle characteristics, and the gelation of the slurry containing the positive electrode active material particle powder The blocking effect of is fully exhibited.

As described above, the water content is changed (increased) by the water exposure treatment in the second step, and the water content is changed (decreased) even by the heat treatment in the third step. The rate of change in the water content of the positive electrode active material particle powder represented by (1) is preferably 0.3 or more and 9.5 or less, and preferably 0.5 or more and 9.0 or less. Since the positive electrode active material particle powder has a rate of change of the water content of 0.3 or more, the characteristics of the non-aqueous electrolyte secondary battery are not deteriorated when used as the positive electrode as a result. Further, since the positive electrode active material particle powder has a change rate of the water content of 9.5 or less, it does not gel during slurry formation and sufficiently acts as a positive electrode of a non-aqueous electrolyte secondary battery. ..

Further, the positive electrode active material particle powder according to the present embodiment preferably has a reduction rate (without unit) of crystal strain represented by the following formula (2) of −0.25 or more and less than 0.
Decrease rate of crystal strain = (S _2- S ₁ ) / S ₁ ... (2)
here,
S ₁ : Crystal strain (%) of lithium composite oxide
S ₂ : Crystal strain (%) of positive electrode active material particle powder
Is.

Crystal strains S ₁ of the lithium composite oxide, a lithium composite oxide obtained through the first step in the manufacturing method according to this embodiment, i.e., a crystal strain of the lithium composite oxide before water exposure process. Meanwhile, the crystal strain S ₂ of the positive electrode active material particles is a positive electrode active material particles obtained through the second step, i.e., the crystal strain of the lithium composite oxide after moisture exposure process, or even a third step This is the crystal strain of the positive electrode active material particle powder obtained through the above process, that is, the lithium composite oxide after the heat treatment.

The crystal strain of the lithium composite oxide is reduced by the water exposure treatment or further heat treatment as compared with that before the water exposure treatment, and the obtained positive electrode active material particle powder is used as the positive electrode of the non-aqueous electrolyte secondary battery. When used in, the effect of increasing the discharge capacity of the non-aqueous electrolyte secondary battery and improving the charge / discharge efficiency is fully exhibited.

As described above, the water content is reduced by the water exposure treatment in the second step, and the water content is also reduced by the heat treatment in the third step, but in each case, it is represented by the above formula (2). The reduction rate of the crystal strain of the positive electrode active material particle powder is preferably −0.25 or more and less than 0, and more preferably −0.20 or more and less than 0. When the reduction rate of the crystal strain of the positive electrode active material particle powder is −0.25 or more, the high temperature cycle characteristics of the non-aqueous electrolyte secondary battery using the positive electrode active material particle powder as the positive electrode do not deteriorate. Further, since the crystal strain reduction rate of the positive electrode active material particle powder is less than 0, that is, the crystal strain is reduced as compared with that before the water exposure treatment, the characteristics of the non-aqueous electrolyte secondary battery can be improved. Sufficient as a positive electrode.

[Non-water electrolyte secondary battery]
The non-aqueous electrolyte secondary battery according to the present embodiment uses the positive electrode active material particle powder according to the present embodiment as the positive electrode as described above. The non-aqueous electrolyte secondary battery will be described.

The non-aqueous electrolyte secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte containing a positive electrode active material made of the positive electrode active material particle powder.

The positive electrode is not particularly limited, but is usually obtained by kneading a positive electrode active material, a conductive agent, and a binder. Examples of the conductive agent include acetylene black, graphite, carbon black, graphite and the like. Examples of the binder include polytetrafluoroethylene and polyvinylidene fluoride.

The negative electrode is made of a negative electrode active material. Examples of the negative electrode active material include metallic lithium, lithium / aluminum alloys, lithium / tin alloys, silicon, silicon / carbon composites, graphite and the like.

Examples of the electrolyte include at least one type of lithium salt such as lithium _{perchlorate (LiClO 4} ) and lithium tetrafluoroborate (LiBF ₄ ), in addition to _{lithium hexafluorophosphate (LiPF 6).} , These can be dissolved in a solvent to obtain an electrolytic solution.

As the solvent of the electrolytic solution, for example, in addition to the combination of ethylene carbonate (EC) and diethyl carbonate (DEC), carbonates having a basic structure of propylene carbonate (PC), dimethyl carbonate (DMC) and the like, and dimethoxy An organic solvent containing at least one of ethers such as ethane (DME) can be used.

[Action]
An important point in the present invention is that the positive electrode active material particle powder according to the present invention obtains an effect by exposing to water to reduce crystal strain and drying the absorbed water. Therefore, in a non-aqueous electrolyte secondary battery using such a positive electrode active material particle powder as a positive electrode, the charge / discharge efficiency is improved and the resistance is improved.

In addition, an important point in the present invention is that in the production method according to the present invention, at least one selected from Li, Ni, Co, Mn, Al and Mg (provided that at least one of Mn and Al is used). The lithium composite oxide containing (including) is subjected to a moisture exposure treatment in an atmosphere in a specific relative humidity range, that is, an atmosphere having a relative humidity of 30% or more and 80% or less, and then heat-treated. Unlike the conventional lithium composite oxide that has not been subjected to the moisture exposure treatment, the non-aqueous electrolyte secondary battery using the positive electrode active material particle powder that has been subjected to the moisture exposure treatment once for the positive electrode is as described above. Charging / discharging efficiency is improved and resistance is also improved.

Hereinafter, the present invention will be specifically described with reference to representative examples and comparative examples of the present invention, but the present invention is not limited to these examples.

(Composition of positive electrode active material particle powder)
The composition of the positive electrode active material particle powder was prepared by heating and dissolving 1.0 g of a sample in 25 ml of a 20% hydrochloric acid solution, cooling the sample, transferring the sample to a 100 ml volumetric flask, and adding pure water to prepare a prepared liquid. ICAP [Optima8300, manufactured by PerkinElmer Co., Ltd.] was used for the measurement, and each element was quantified and determined.

(Compound phase of positive electrode active material particle powder)
XRD was used to identify the compound phase of the positive electrode active material particle powder. The XRD is an X-ray diffractometer [SmartLab, manufactured by Rigaku Co., Ltd.], the radiation source is CuKα, the acceleration voltage and current are 45 kV and 200 mA, respectively, and 2θ / θ is in the range of 15 ° to 122 °, and the slit 2 XRD diffraction was obtained by performing 1.2 ° / min step scans in increments of / 3, 0.02 °.

(Moisture content)
The water content (ppm) of each compound was the water content generated up to 150 ° C. based on the Karl Fischer method (potentiometric titration method).

(Compression density of positive electrode active material particle powder)
The compression density (g / cm ³ ) of the positive electrode active material particle powder was taken as a value when 5 g of the positive electrode active material particle powder was placed in a mold of Φ15 mm ^{and pressurized to 2 t / cm 2.}

(Amount of residual lithium in positive electrode active material particle powder)
The amount of residual lithium in the positive electrode active material particle powder was measured using the Walder method. Specifically, 20 g of positive electrode active material particle powder was added to 100 ml of water, and the mixture was stirred at room temperature for 20 minutes, and then the solid content was filtered off and removed to obtain 0.2 N of the supernatant. It was determined by titration with hydrochloric acid. On the pH curve drawn by plotting the titration amount (ml) on the horizontal axis and the pH of the supernatant on the vertical axis, the two points with the largest tilt are the first titration point and the second titration point from the one with the smallest titration. The titration points were set, and the respective amounts were calculated using the following formulas from the titration quantification at these points to obtain the residual lithium amount. In Table 2 below, it is shown as the amount of residual lithium (ppm). The abbreviations in the calculation formula are as follows.
T ₁ : Titration up to the first titration point (ml)
T ₂ : Titration up to the second titration point (ml)
C _HCl : Concentration of hydrochloric acid used for titration (mol / l)
F _HCl : Hydrochloric acid factor used for titration M _LiOH : Molecular weight of lithium hydroxide M _Li2CO3 : Molecular weight of lithium carbonate W: Weight of positive electrode active material particle powder (g)

Amount of residual lithium hydroxide (% by weight)
= {T ₂ -2 x (T _2- T ₁ )} x C _HCl x F _HCl x M _LiOH x 2 x 100 / (W x 1000)
Amount of residual lithium carbonate (% by weight)
= (T _2- T ₁ ) × C _HCl × F _HCl × M _Li2CO3 × 2 × 100 / (W × 1000)
The amount of residual lithium was calculated by converting the amount of residual lithium hydroxide into the amount of residual lithium carbonate and adding it to the original amount of residual lithium carbonate.

<Making a coin cell>
The coin cell related to the battery evaluation was produced as follows. First, 90% by weight of the lithium composite oxide as the positive electrode active material particle powder according to each of the examples, comparative examples, and reference examples described later, and 3% by weight of acetylene black and 3% by weight of graphite as the conductive agent are bound. After mixing 4% by weight of polyvinylidene fluoride dissolved in N-methylpyrrolidone as an agent, the mixture was applied to an Al metal foil and dried at 120 ° C. to prepare a sheet. This sheet was punched to 14 mmΦ and then ^{crimped at 1.5 t / cm 2} to obtain a positive electrode. The negative electrode was metallic lithium having a thickness of 500 μm punched to 16 mmΦ. The electrolytic solution was a _{solution in which EC and DMC in which 1 mol / L LiPF 6} was dissolved were mixed at an EC: DMC = 1: 2 (volume ratio). A 2032 type coin cell was produced using these positive electrodes, negative electrodes, and an electrolytic solution.

(Discharge capacity and charge / discharge efficiency of non-aqueous electrolyte secondary battery)
Using the coin cell, charging was performed at a current density of 0.1 C rate from a voltage of 3.0 V to 4.3 V (cc-cv) in an environment of 25 ° C., and the charge capacity was measured. Then, under the same environment, discharge was performed from a voltage of 4.3 V to 3.0 V (cc) at a current density of 0.1 C rate, and the discharge capacity (mAh / g) was measured. The charge / discharge efficiency (%) was obtained from the ratio of the discharge capacity to the charge capacity (discharge capacity / charge capacity).

(Internal resistance of non-aqueous electrolyte secondary battery)
An impedance analyzer [1252 type, manufactured by Solartron] was used to assemble a symmetric cell with a positive electrode, and impedance measurement was performed. A Core-Cole plot was obtained as an impedance measurement result.

(High temperature cycle characteristics of non-aqueous electrolyte secondary batteries)
Using the coin cell, charging at a current density of 0.5 C rate from a voltage of 3.0 V to 4.3 V (cc-cv) and a voltage of 4.3 V to 3.0 V (cc) in an environment of 60 ° C. The ratio of the 100th discharge capacity to the 1st discharge capacity (maintenance rate = 100th discharge capacity / 1st discharge capacity) when discharging at a current density of 1C rate is repeated 100 times is obtained, and the high temperature is obtained. The cycle characteristic (%) was used.

(Crystal strain of positive electrode active material particle powder)
Using XRD diffraction of the positive electrode active material particle powder obtained in the same manner as in the identification of the phase of the compound, Rietveld analysis was performed to calculate the crystal strain (%). Then, the positive electrode active material particle powder was stored in a high humidity bath at a predetermined humidity, and then Rietveld analysis was performed using the XRD diffraction obtained again. For Rietveld analysis, for example, "RA Young, ed.," The Rietveld Method ", Oxford University Press (1992)" was referred to.

<Reference example 1>
First, nickel sulfate, cobalt sulfate, and manganese sulfate are weighed so that the ratio of each element (Ni / Co / Mn) is 5.0 / 2.0 / 3.0 in terms of molar ratio, and these are added to water. It was dissolved to obtain an aqueous solution. A mixture of a caustic soda solution and an ammonia solution was added to this aqueous solution as a precipitating agent, and the mixture was stirred and mixed, and nickel sulfate, cobalt sulfate, and manganese sulfate were co-precipitated in a wet manner. After the reaction product was obtained by overflowing, it was washed with water and dried to obtain a composite compound precursor.

Next, the lithium carbonate and the obtained composite compound precursor were placed in a mortar for 1 hour so that the ratio of Li to Ni, Co and Mn [Li / (Ni + Co + Mn)] was 1.04. Mixing gave a uniform mixture. The obtained mixture was placed in an alumina crucible, held at 930 ° C. for 5 hours and fired in an oxidizing atmosphere to obtain [Li _1.04 (Ni _0.5 Co _0.2 Mn _0.3 ) O ₂ ]. A lithium composite oxide particle powder was obtained.

<Example 1>
The lithium composite oxide particle powder obtained in Reference Example 1 was placed in a constant temperature and humidity chamber set at a relative humidity of 40% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Example 2>
The lithium composite oxide particle powder obtained in Reference Example 1 was placed in a constant temperature and humidity chamber set at a relative humidity of 60% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Example 3>
The lithium composite oxide particle powder obtained in Reference Example 1 was placed in a constant temperature and humidity chamber set at a relative humidity of 30% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Example 4>
The lithium composite oxide particle powder obtained in Reference Example 1 was placed in a constant temperature and humidity chamber set at a relative humidity of 80% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Example 5>
The lithium composite oxide particle powder obtained in Reference Example 1 was placed in a constant temperature and humidity chamber set at a relative humidity of 70% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Example 6>
The lithium composite oxide particle powder obtained in Reference Example 1 was placed in a constant temperature and humidity chamber set at a relative humidity of 60% and a temperature of 30 ° C. for 10 minutes, and subjected to moisture exposure treatment.

Next, the lithium composite oxide particle powder after the moisture exposure treatment was placed in a firing furnace set at a temperature of 300 ° C. for 3 hours and heat-treated to obtain a positive electrode active material particle powder.

<Example 7>
In Example 6, the lithium composite oxide particle powder after the moisture exposure treatment was placed in a firing furnace set at a temperature of 200 ° C. for 3 hours and heat-treated, and the positive electrode was the same as in Example 6. Active material particle powder was obtained.

<Example 8>
In Example 6, the lithium composite oxide particle powder after the moisture exposure treatment was placed in a firing furnace set at a temperature of 400 ° C. for 3 hours and heat-treated, and the positive electrode was the same as in Example 6. Active material particle powder was obtained.

<Reference example 2>
First, nickel sulfate, cobalt sulfate, and manganese sulfate are weighed so that the ratio of each element (Ni / Co / Mn) is 1.0 / 1.0 / 1.0 in terms of molar ratio, and these are added to water. It was dissolved to obtain an aqueous solution. A mixture of a caustic soda solution and an ammonia solution was added to this aqueous solution as a precipitating agent, and the mixture was stirred and mixed, and nickel sulfate, cobalt sulfate, and manganese sulfate were co-precipitated in a wet manner. After the reaction product was obtained by overflowing, it was washed with water and dried to obtain a composite compound precursor.

Next, the ratio of lithium carbonate and the obtained composite compound precursor to Li and Ni, Co and Mn was 1.08, and the mixture was placed in a mortar for 1 hour. Mixing gave a uniform mixture. The obtained mixture was placed in an alumina crucible, held at 960 ° C. for 5 hours and fired in an oxidizing atmosphere to obtain [Li _1.08 (Ni _0.33 Co _0.33 Mn _0.33 ) O ₂ ]. A lithium composite oxide particle powder was obtained.

<Example 9>
The lithium composite oxide particle powder obtained in Reference Example 2 was placed in a constant temperature and humidity chamber set at a relative humidity of 60% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Reference example 3>
First, nickel sulfate, cobalt sulfate, and manganese sulfate are weighed so that the ratio of each element (Ni / Co / Mn) is 6.0 / 2.0 / 2.0 in terms of molar ratio, and these are added to water. It was dissolved to obtain an aqueous solution. A mixture of a caustic soda solution and an ammonia solution was added to this aqueous solution as a precipitating agent, and the mixture was stirred and mixed, and nickel sulfate, cobalt sulfate, and manganese sulfate were co-precipitated in a wet manner. After the reaction product was obtained by overflowing, it was washed with water and dried to obtain a composite compound precursor.

Next, the lithium hydroxide monohydrate and the obtained composite compound precursor were arranged so that the ratio of Li to Ni, Co and Mn [Li / (Ni + Co + Mn)] was 1.02. , The mixture was mixed in a mortar for 1 hour to obtain a uniform mixture. The obtained mixture was placed in an alumina crucible, held at 900 ° C. for 5 hours and fired in an oxidizing atmosphere to obtain [Li _1.02 (Ni _0.6 Co _0.2 Mn _0.2 ) O ₂ ]. A lithium composite oxide particle powder was obtained.

<Example 10>
The lithium composite oxide particle powder obtained in Reference Example 3 was placed in a constant temperature and humidity chamber set at a relative humidity of 60% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Reference example 4>
First, nickel sulfate, cobalt sulfate, and sodium aluminate are weighed so that the ratio of each element (Ni / Co / Al) is 8.0 / 1.5 / 0.5 in terms of molar ratio, and these are weighed with water. To obtain an aqueous solution. A mixture of a caustic soda solution and an ammonia solution was added to this aqueous solution as a precipitating agent, and the mixture was stirred and mixed, and nickel sulfate, cobalt sulfate, and sodium aluminate were co-precipitated in a wet manner. After the reaction product was obtained by overflowing, it was washed with water and dried to obtain a composite compound precursor.

Next, the lithium hydroxide monohydrate and the obtained composite compound precursor were arranged so that the ratio of Li to Ni, Co and Al [Li / (Ni + Co + Al)] was 1.01. , The mixture was mixed in a mortar for 1 hour to obtain a uniform mixture. The obtained mixture is placed in an alumina crucible, held at 740 ° C. for 5 hours and fired in an oxidizing atmosphere to obtain [Li _1.01 (Ni _0.80 Co _0.15 Al _0.05 ) O ₂ ]. A lithium composite oxide particle powder was obtained.

<Example 11>
The lithium composite oxide particle powder obtained in Reference Example 4 was placed in a constant temperature and humidity chamber set at a relative humidity of 60% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Comparative Example 1>
The lithium composite oxide particle powder obtained in Reference Example 1 was placed in a constant temperature and humidity chamber set at a relative humidity of 20% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got

<Comparative Example 2>
The lithium composite oxide particle powder obtained in Reference Example 1 was placed in a constant temperature and humidity chamber set at a relative humidity of 90% and a temperature of 30 ° C. for 10 minutes, subjected to moisture exposure treatment, and subjected to a positive electrode active material particle powder. Got The positive electrode active material particle powder was gelled during slurry formation, and could not be used as the positive electrode of a non-aqueous electrolyte secondary battery.

The characteristics of the lithium composite oxide particle powder and the positive electrode active material particle powder obtained in Examples 1 to 11, Comparative Examples 1 to 2, and Reference Examples 1 to 4 were each examined according to the above method. The results are shown in Tables 1 and 2 below. The composition of the positive electrode active material particle powder, the conditions for moisture exposure treatment, the conditions for heat treatment, and the like are summarized in Table 1 below.

Further, for the positive electrode active material particle powder obtained in Example 2, the phase was identified according to the above method. The results are shown in FIG. Further, in Example 1 and Reference Example 1, the impedance of the non-aqueous electrolyte secondary battery was measured according to the above method, and a Cole-Cole plot was obtained. This is shown in FIG.

As shown in the conditions and results of Table 1 and the results of Table 2, the positive electrode active material particle powder obtained by subjecting the lithium composite oxide to water exposure treatment as in Examples 1 to 5 and 9 to 11 is also an example. The positive electrode active material particle powder obtained by further heat-treating such as 6 to 8 also has a change rate of the water content in a specific range such as 0.3 or more and 9.5 or less, and is -0.25. It has a reduction rate of crystal strain in a specific range such as more than 0 and less than 0.

As shown in the conditions in Table 1 and the results in Table 2, comparison between Examples 1 to 5 and Reference Example 1 and Comparative Examples 1 and 2, comparison between Example 9 and Reference Example 2, and Example 10 and Reference Example 3 From the comparison of Examples 11 and 4 and the comparison of the above, when the lithium composite oxide was subjected to the moisture exposure treatment in an atmosphere of a relative humidity of 30% or more and 80% or less as in each example, each Compared to the case where the moisture exposure treatment was not applied as in the reference example, or when the lithium composite oxide was subjected to the moisture exposure treatment in an atmosphere with a relative humidity of less than 30% or more than 80% as in each comparative example. It can be seen that the discharge capacity of the non-aqueous electrolyte secondary battery has increased (value increases) and the charge / discharge efficiency has improved (value increases).

Further, when the lithium composite oxide after the moisture exposure treatment is further heat-treated as in Examples 6 to 8, the positive electrode active material particle powder is compared with Example 2 which is not heat-treated. The water content is significantly reduced. As a result, in Examples 6 to 8, the characteristics such as reduction of crystal strain of the positive electrode active material particle powder and the discharge capacity and charge / discharge efficiency of the non-aqueous electrolyte secondary battery are different from those of Example 2 in which the heat treatment is not applied. It can be seen that the high temperature cycle characteristics are maintained to almost the same level and the high temperature cycle characteristics are improved to almost the same level as in Reference Example 1 before the water exposure treatment.

Further, as shown in FIG. 2, the arc drawn by the Core-Cole plot of the non-aqueous electrolyte secondary battery of Example 1 is smaller than that of the non-aqueous electrolyte secondary battery of Reference Example 1, and the lithium composite oxide is formed. It can be seen that the resistance of the non-aqueous electrolyte secondary battery of Example 1 is improved by using the positive electrode active material particle powder subjected to the water exposure treatment for the positive electrode.

The positive electrode active material particle powder according to the present invention is suitable as an active material used for the positive electrode of a non-aqueous electrolyte secondary battery.

Claims (8)

A lithium composite oxide having a layered rock salt structure and containing Li, Ni, Co, and at least one selected from Mn, Al, and Mg (provided that at least one of Mn and Al is contained) is used. a name Ru positive electrode active material particles Te,
The positive electrode active material particle powder has a composition formula:
Li _a (Ni _p Co _q Mn _r Al _1-p-q-r Mg _u ) O ₂
It has a basic composition represented by
In the composition formula, 0.96 ≦ a ≦ 1.15, 0 <p ≦ 0.97, 0 <q ≦ 0.50, satisfying p + q <1.00, and the positive electrode active material particle powder. Is 0 <r ≦ 0.50 when Mn is contained, and 0 <(1-p−q−r) ≦ 0.20 when the positive electrode active material particle powder contains Al, and the positive positive active material particle powder. When contains Mg, 0 <u ≦ 0.20, and
In addition to the Ni, Co, Mn, Al, and Mg, the positive electrode active material particle powder is derived from P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W. It optionally contains at least one selected metal and
When the positive electrode active material particle powder contains at least one metal selected from the P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W, the at least. One metal is replaced with a part of at least one selected from the Ni, Co, Mn, Al, and Mg in the lithium composite oxide, or is an aggregated secondary of the lithium composite oxide. It is covered on the surface and boundary of the particles,
The lithium composite oxide is a composite oxide that has not been exposed to moisture.
The positive electrode active material particle powder is a composite oxide that has been subjected to moisture exposure treatment in an atmosphere having a relative humidity of 30% or more and 80% or less, and contains 300 ppm or more and 1200 ppm or less. Has a water content,
Positive electrode active material particle powder characterized in that the rate of change (without unit) of the water content represented by the following formula (1) is 0.3 or more and 9.5 or less.
Rate of change in water content = | (W2-W1) / W1 | ... (1)
here,
W1: Moisture content of lithium composite oxide (ppm)
W2: Moisture content (ppm) of positive electrode active material particle powder
Is. The positive electrode active material particle powder according to claim 1, wherein the reduction rate (without unit) of the crystal strain represented by the following formula (2) is −0.25 or more and less than 0.
Reduction rate of crystal strain = (S2-S1) / S1 ... (2)
here,
S1: Crystal strain (%) of lithium composite oxide
S2: Crystal strain (%) of positive electrode active material particle powder
Is. The method for producing a positive electrode active material particle powder according to claim 1 or 2.
It has at least the following first and second steps,
In the first step, the lithium compound, the nickel compound, the cobalt compound, and at least one compound selected from the manganese compound, the aluminum compound, and the magnesium compound (provided to include at least one of the manganese compound and the aluminum compound). , Arbitrarily preparing a compound of at least one metal selected from P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W to prepare a nickel compound and After preparing a composite compound precursor using a cobalt compound and at least one compound selected from a manganese compound, an aluminum compound and a magnesium compound (provided that at least one of the manganese compound and the aluminum compound is included), the composite is prepared. A mixture obtained by mixing a lithium compound and optionally at least one compound selected from a manganese compound, an aluminum compound and a magnesium compound as a compound precursor was fired to obtain Li, Ni, Co and Li. At least one selected from Mn, Al and Mg (including at least one of Mn and Al) and optionally P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, nb, and lithium composite oxide containing at least one metal selected from W to prepare,
In the second step, the lithium composite oxide prepared in the first step, and facilities moisture exposure process in the following atmosphere of 80% relative humidity of 30% or more, to prepare a composite oxide of moisture exposure processed < A method for producing a positive electrode active material particle powder, which is characterized by the above. Wherein the composite oxide of moisture exposure treated prepared in the second step, further comprising a third step of performing heat treatment, the positive electrode active material particle producing method of powder according to claim 3. The method for producing a positive electrode active material particle powder according to claim 4 , wherein the heat treatment is performed at 180 ° C. or higher and 400 ° C. or lower. The complex compound precursor is prepared using a compound of at least one metal selected from P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and W. The method for producing a positive electrode active material particle powder according to any one of claims 3 to 5. Wherein the composite compound precursor, the P, Ca, Ti, Y, Sn, Bi, Ce, Zr, La, Mo, Sc, Nb, and dry mixing the compound of at least one metal selected from W, The method for producing a positive electrode active material particle powder according to any one of claims 3 to 5. A non-aqueous electrolyte secondary battery using the positive electrode active material particle powder according to claim 1 or 2 for the positive electrode.

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