JPH11317226A - Positive active material for lithium secondary battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the capacity drop in a short term attendant on repeated charge/discharge cycles by constituting an positive active material with a compound having a specified element composition and monoclinic system crystal structure. SOLUTION: The composition formula of a compound constituting a positive active material is represented by Nax Li1-x By Mn1-y O2 , wherein B is at least one of Ti, V, Cr, Fe, Ni, Cu, and Al, 0<x<1, and 0<y<1. This compound is manufactured in such a way that a compound having a composition formula of Nax By Mn1-y O2 is prepared, a lithium bromide solution or a lithium chloride solution having a concentration of 0.05-5 mol/l is prepared by dissolving lithium bromide or lithium chloride in an n-hexanol in a nitrogen flow, the compound is added to the solution so as to have the composition of 4<=Li/Na<=20, and they are stirred and reacted at 135-145 deg.C in a nitrogen flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode active material for a lithium secondary battery, and more particularly to a method for producing a positive electrode active material for a lithium secondary battery. The present invention relates to a lithium secondary battery manufactured and used.

[0002]

2. Description of the Related Art In general, a lithium secondary battery is partitioned by providing a separator 1 at a central portion of a container 4 containing an electrolytic solution 5 as shown in a sectional view of FIG. The structure is such that the positive electrode 2 is immersed in the electrolytic solution 5 and attached, and the negative electrode 3 is attached to the other side of the separator 1 by immersing it in the electrolytic solution. The positive electrode 2 has a structure in which a slurry containing an active material is applied to or impregnated on an Al mesh plate and then dried by heating and attached thereto, while the negative electrode 3 is made of graphite or metallic Li. .

The active material adhered to the positive electrode 2 is conventionally
LiCoO ₂ or LiNiO ₂ was used,
In recent years, it has been reported that LiMnO ₂ having a monoclinic crystal structure can be used as a positive electrode active material of a lithium secondary battery (A. Robaert Armstrong &
Peter G. Bruce "NATURE" VO
L 381.6 JUNE 1996 p499-50
0). A lithium secondary battery is manufactured by using the LiMnO ₂ compound having the monoclinic crystal structure as a positive electrode active material, and when charge and discharge are repeated, a spinel phase is generated and the discharge capacity of the lithium secondary battery decreases. It is known. Further, part of Mn in LiMnO ₂ is converted to C
LiCo _x Mn having a monoclinic crystal structure substituted with o
It has been reported that the _{1-xO 2} compound can further prevent the formation of a spinel phase due to repeated charge and discharge, and is effective as a positive electrode active material of a lithium secondary battery (Pet).
erG. Bruce et al., 3 lecture materials for "International Open Seminar", March 16, 1998).

[0004]

However, LiCo _x Mn having a monoclinic crystal structure in which Mn is partially substituted by LiMnO ₂ or Co having a monoclinic crystal structure as described above.
A lithium secondary battery fabricated using a _1-x O ₂ compound as a positive electrode active material, even though charge and discharge are repeated, the formation of a spinel phase is less likely than in the past, but the formation of a spinel phase is sufficiently prevented. Therefore, a positive electrode active material for a lithium secondary battery in which a spinel phase is less likely to be generated has been demanded.

[0005]

Means for Solving the Problems Accordingly, the present inventors have:
Even if the number of times of charging and discharging increases, it is more difficult to form a spinel phase.
And therefore the discharge capacity is not likely to decrease.
As a result of the development to obtain the positive electrode active material of the secondary battery,
LiMnO with conventional monoclinic crystal structure_TwoAt
Part of Li was replaced by Na, and part of Mn was further replaced by B [
However, B is Ti, V, Cr, Fe, Ni, Cu and A
at least one of the above (hereinafter the same)]
The formula is Na_xLi _1-xB_YMn_1-YO_Two(However, 0 <x
<1, 0 <y <1) and has a monoclinic crystal structure
Compound that is incorporated into the positive electrode as a positive electrode active material
Rechargeable batteries have a spinel phase
Low generation, so short time even after repeated charge and discharge
With, the discharge capacity of the lithium secondary battery does not decrease,
That's the finding.

The present invention has been made based on such findings, and (1) a composition formula of Na _x Li ₁ -xB _Y Mn ₁ -YO ₂ (where 0 <x <1, 0 < y <1) and a positive electrode active material for a lithium secondary battery comprising a compound having a monoclinic crystal structure.

The composition formula (1) is Na _x Li _1-x
BY Mn _{1-YO 2} (where 0 <x <1, 0 <y <1)
A lithium secondary battery positive electrode active material comprising a compound represented by the formula and having a monoclinic crystal structure has a composition formula of Na _{x BY} M
A compound satisfying n _{1 -Y} O ₂ (where 0 <x <1, 0 <y <1) is prepared, and Li bromide or Li chloride is dissolved in n-hexanol in a nitrogen stream to obtain a concentration of 0. .05-
A 5 mol / l Li bromide solution or a Li chloride solution was prepared, and the composition formula was Na _{x BY} Mn _{1-YO 2} (where 0
<X <1, 0 <y <1),
It can be manufactured by adding to the i solution or the Li chloride solution so that 4 ≦ Li / Na ≦ 20, and stirring and reacting in a nitrogen stream while maintaining the temperature at 135 to 145 ° C.

Accordingly, the present invention provides: (2) a composition formula of Na _{x BY} Mn _{1-YO 2} (where 0 <
x <1, 0 <y <1), and n
Dissolving Li bromide or Li chloride in hexanol in a nitrogen stream to prepare a Li bromide solution or Li chloride solution having a concentration of 0.05 to 5 mol / l, wherein the composition formula is Na _x B
A compound represented by _Y Mn _{1-YO 2} (where 0 <x <1, 0 <y <1) is added to the Li bromide solution or the Li chloride solution so that 4 ≦ Li / Na ≦ 20. And temperature: 1
A method for producing a positive electrode active material for a lithium secondary battery in which a reaction is carried out by stirring in a nitrogen stream while maintaining the temperature at 35 to 145 ° C.

The positive electrode active material for a lithium secondary battery according to the present invention
Has a composition formula of Na_xB _YMn_1-YO_Two(T
However, the compound represented by 0 <x <1, 0 <y <1)
Sodium carbonate, manganese oxide, and chlorides of B, vinegar
Salts, oxides, chlorites, etc. are compounded, mixed, molded,
It is made by firing. When B is Al, AlCl_Three,
Al acetate is used, and when B is Ti, TiCl_ThreeTo
And when B is V, V_TwoO_Three, VCl_Threeuse
And when B is Cr,_Three, Cr_TwoO_Three,vinegar
Acid Cr is used, and when B is Fe, FeOOH is used.
When B is Ni, use NiOOH or Ni acetate.
When B is Cu, CuO is used.

In order to produce the positive electrode active material for a lithium secondary battery according to the present invention, Li bromide or Li chloride is dissolved in n-hexanol in a nitrogen stream to obtain a concentration of 0.1.
A Li bromide solution or a Li chloride solution of 0.5 to 5 mol / l is prepared.

The compound represented by the composition formula Na _{x BY} Mn _{1-YO 2} (where 0 <x <1, 0 <y <1) is added to the Li bromide solution or Li chloride solution in an amount of 4 ≦. Li / Na ≦
When the mixture is stirred and reacted in a nitrogen stream while maintaining the temperature at 135 to 145 ° C., the composition formula is Na _x Li _{1-x BY} Mn _1- YO ₂ (where 0 < x <
The compound represented by 1, 0 <y <1) is obtained.

In the Li bromide solution or the Li chloride solution, the composition formula is Na _{x BY} Mn _{1-YO 2} (where 0 <x <1,
The reason why the compound represented by 0 <y <1) is added to the Li bromide solution or the Li chloride solution so as to satisfy 4 ≦ Li / Na ≦ 20 is that when Li / Na is less than 4, ions of Li and Na The exchange reaction does not proceed sufficiently and a product containing Li cannot be obtained, which is not preferable.
Is exceeded, there is no difference in the Li concentration in the obtained product.
This is because it is not preferable because the effect of increasing / Na is not obtained.

Further, the Li bromide solution or Li chloride solution may be used.
The composition formula is Na in the liquid._xB_YMn_1-YO _Two(However, 0 <x
<1, 0 <y <1), the compound represented by the formula
Solution or Li chloride solution, temperature: 135-145
Reason to react by stirring in nitrogen stream while keeping at ℃
Is sufficient for Li and Na ions at temperatures below 135 ° C
On the other hand, it is not preferable because the exchange reaction rate cannot be obtained.
When the temperature exceeds 45 ° C., it approaches the boiling point of n-hexanol,
Since boiling starts from the bottom of the reaction vessel,
It depends.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Na ₂ CO ₃ , MnO ₂ , AlC
l ₃ , TiCl ₃ , VCl ₃ , CrCl ₃ , FeOO
H, NiOOH, and CuO were prepared, blended, and the resulting blended powder was blended with 100 g of the blended powder: 100 g of a YSZ ball having a diameter of 5 mm: 100 g, and ethanol: 2
The mixture was filled into a ball mill at a ratio of 00 ml, mixed for 3 hours, dried, molded, and placed in a nitrogen atmosphere at a temperature of 700 ° C.
Firing was performed under the conditions of holding for 10 hours, and the step of firing after molding was repeated three times to produce host material compounds A to I having the composition formulas shown in Table 1.

[0015]

[Table 1]

On the other hand, Li bromide or Li chloride was dissolved in n-hexanol in a nitrogen stream to prepare Li chloride solutions having the concentrations shown in Tables 2 and 3.

The host material compounds A to I having the compositional formulas shown in Table 1 were added to Li chloride solutions having the concentrations shown in Tables 2 and 3 so that Li / Na had the values shown in Tables 2 and 3. The mixture was stirred and reacted in a nitrogen stream while maintaining the temperature shown in Tables 2 and 3 and methanol was added thereto for 150 m
l, followed by filtration, further adding 150 ml of methanol and washing to prepare an active material, and by repeating the same operation three times on the obtained active material, the active material is composed of compounds of the composition formulas shown in Tables 2 and 3. Positive electrode active materials for lithium secondary batteries of the present invention (hereinafter, referred to as active materials of the present invention) 1 to 14 were produced. X-ray diffraction of the active materials 1 to 14 of the present invention revealed that each had a monoclinic crystal structure.

Furthermore, for comparison, the positive electrode active material for a conventional lithium secondary battery comprising a LiMnO ₂ (hereinafter, conventional as active material) was 1 and LiCo _0.1 of Mn _0.9 O ₂ prior active material consists of) 2 prepared .

Solvent (acetone): 2 g, Binder (PVdF: polyvinylidene fluoride): 0.8 g for each of 0.84 g of each of the obtained active materials 1 to 14 of the present invention and conventional active materials 1 to 2.
224 g, carbon powder: 0.088 g, were added to prepare a slurry, and this slurry was processed into a film, and the film was heated at a temperature of 130 ° C. and a pressure of 10
Heat-press bonding under the condition of 0 kgf / cm ₂ , excluding terminals 1c
A positive electrode having 30 mg of the active material attached to an Al mesh having a size of mx 1 cm was prepared.

These positive electrodes are immersed in an electrolytic solution composed of an inorganic lithium salt and a carbonate ester solvent.
A metal lithium plate having a size of mx 1 cm is immersed in the electrolyte,
A three-electrode cell is configured by immersing a reference electrode made of a metal lithium plate having a size of 1 cm × 1 cm in the electrolyte between the positive electrode and the counter electrode and arranging the same. The value of the positive electrode discharge capacity (mAh / g) with respect to the number of times of charge / discharge was measured, and the results are shown in Table 4.

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

As shown in Table 4, the active materials 1 to 5 of the present invention
The lithium secondary battery cell obtained by incorporating the positive electrode manufactured using No. 14 does not greatly reduce the discharge capacity even if charging and discharging are repeated 50 times, whereas the conventional active materials 1 and 2 It can be seen that the discharge capacity of the lithium secondary battery cell obtained by incorporating the positive electrode manufactured by use is greatly reduced.

[0025]

As described above, the positive electrode active material of the present invention can provide a lithium secondary battery that can be used for a longer time than before, and can greatly contribute to the development of the electric and electronic industries. Things.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic cross-sectional explanatory view showing a structure of a lithium secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Separator 2 Positive electrode 3 Negative electrode 4 Container 5 Electrolyte

Claims (10)

[Claims] 1. B is Ti, V, Cr, Fe, Ni, Cu
And at least one of Al (the same applies hereinafter), the composition formula is represented by Na _x Li _{1-x BY} Mn _{1-YO 2} (where 0 <x <1, 0 <y <1). A positive electrode active material for a lithium secondary battery, comprising a compound having a monoclinic crystal structure. 2. A compound having a composition formula of Na _{x BY} Mn _{1-YO 2} (where 0 <x <1, 0 <y <1) is prepared. On the other hand, Li-bromide or n-hexanol is added to n-hexanol. was dissolved chloride Li in a stream of nitrogen concentration to produce a 0.05 to 5 mol / l bromide Li solution or chloride Li solution, the composition formula _{Na x B Y Mn 1-Y} O 2 ( where 0 <X
The compound represented by <1, 0 <y <1) is added to the Li bromide solution or the Li chloride solution so that 4 ≦ Li / Na ≦ 20, and the temperature is maintained at 135 to 145 ° C. and the nitrogen gas flow is maintained. 2. The reaction is carried out by stirring in a reactor.
The method for producing a positive electrode active material for a lithium secondary battery according to the above. 3. A lithium secondary battery, comprising: preparing a positive electrode using the positive electrode active material for a lithium secondary battery according to claim 1; and incorporating the positive electrode. 4. Compounding, mixing, shaping sodium carbonate, manganese oxide, and chloride or acetate of Al;
After calcination, the composition formula is Na _x Al _Y Mn _1-Y O ₂ (however,
A compound satisfying 0 <x <1, 0 <y <1) is prepared. On the other hand, Li-bromide or Li-chloride is dissolved in n-hexanol in a nitrogen gas stream to give a odor having a concentration of 0.05 to 5 mol / l. A Li solution or a Li chloride solution is prepared, and the composition formula is Na _x Al _Y Mn ₁ -YO ₂ (where 0 <
x <1, 0 <y <1) with the compound represented by Li bromide
The composition formula is Na _x Li ₁ , which is added to the solution or the Li chloride solution so as to satisfy 4 ≦ Li / Na ≦ 20, and is stirred and reacted in a nitrogen stream while maintaining the temperature at 135 to 145 ° C. _-x Al _Y Mn _{1-YO 2} (where 0 <x
A method for producing a positive electrode active material for a lithium secondary battery, comprising a compound represented by <1, 0 <y <1) and having a monoclinic crystal structure. 5. A composition of Na _x Ti _Y Mn ₁ -YO ₂ (where 0 <x <1), wherein sodium carbonate, manganese oxide and chloride of Ti are compounded, mixed, molded and fired. ,
On the other hand, a compound satisfying 0 <y <1) is prepared. On the other hand, Li bromide or Li chloride is dissolved in n-hexanol in a nitrogen stream to obtain a Li bromide solution or a Li chloride having a concentration of 0.05 to 5 mol / L. A solution was prepared, and the composition formula was Na _x Ti _Y Mn ₁ -YO ₂ (where 0 <
x <1, 0 <y <1) with the compound represented by Li bromide
The composition formula is Na _x Li ₁ , which is added to the solution or the Li chloride solution so as to satisfy 4 ≦ Li / Na ≦ 20, and is stirred and reacted in a nitrogen stream while maintaining the temperature at 135 to 145 ° C. _-x Ti _Y Mn _1-Y O ₂ (where 0 <x
A method for producing a positive electrode active material for a lithium secondary battery, comprising a compound represented by <1, 0 <y <1) and having a monoclinic crystal structure. 6. A composition comprising Na carbonate, manganese oxide, and an oxide or chloride of V is mixed, mixed, molded, and fired to obtain a composition formula of Na _x V _Y Mn ₁ -YO ₂ (where 0 <
x <1, 0 <y <1), and Li-bromide or Li-chloride is dissolved in n-hexanol in a stream of nitrogen to obtain a Li bromide having a concentration of 0.05 to 5 mol / l. A solution or a Li chloride solution is prepared, and the composition formula is Na _x V _Y Mn ₁ -YO ₂ (where 0 <x
The compound represented by <1, 0 <y <1) is added to the Li bromide solution or the Li chloride solution so that 4 ≦ Li / Na ≦ 20, and the temperature is maintained at 135 to 145 ° C. and the nitrogen gas flow is maintained. stirred composition formula, comprising reacting with the _{Na x Li 1-x V Y} Mn 1-Y O 2 at medium (where, 0 <x <
1, a method for producing a positive electrode active material for a lithium secondary battery, comprising a compound represented by 0 <y <1) and having a monoclinic crystal structure. 7. A sodium carbonate, manganese oxide, and
Mix and mix Cr chloride, oxide or acetate,
Molded and fired, the composition formula is Na_xCr_YMn _1-YO
_Two(Where 0 <x <1, 0 <y <1)
On the other hand, Li-bromide or Li-chloride is
Dissolves in air stream and has a concentration of 0.05-5 mol / l odor
To prepare a Li solution or a Li chloride solution, wherein the composition formula is Na_xCr_YMn_1-YO_Two(However, 0 <
x <1, 0 <y <1) with the compound represented by Li bromide
4 ≦ Li / Na ≦ 20 in solution or Li chloride solution
While maintaining the temperature at 135-145 ° C.
A composition formula characterized by stirring and reacting in a stream of air
Is Na_xLi_1-xCr_YMn_1-YO_Two(However, 0 <x
<1, 0 <y <1) and has a monoclinic crystal structure
Of positive electrode active material for lithium secondary battery composed of compound
Method. 8. A composition comprising Na _x Fe _Y Mn ₁ -YO ₂ (where 0 <x <1), wherein sodium carbonate, manganese oxide, and a ferrite salt are blended, mixed, molded and fired. , 0
A compound that satisfies <y <1) is prepared. On the other hand, Li bromide or Li chloride is dissolved in n-hexanol in a nitrogen stream to obtain a Li bromide solution or Li chloride solution having a concentration of 0.05 to 5 mol / l. And the composition formula is Na _x Fe _Y Mn ₁ -YO ₂ (where 0 <
x <1, 0 <y <1) with the compound represented by Li bromide
The composition formula is Na _x Li ₁ , which is added to the solution or the Li chloride solution so as to satisfy 4 ≦ Li / Na ≦ 20, and is stirred and reacted in a nitrogen stream while maintaining the temperature at 135 to 145 ° C. _-x Fe _Y Mn _{1-YO 2} (where 0 <x
A method for producing a positive electrode active material for a lithium secondary battery, comprising a compound represented by <1, 0 <y <1) and having a monoclinic crystal structure. 9. A mixture of sodium carbonate, manganese oxide, and a hydroxide or Ni nitrate of Ni, mixed, molded and calcined to obtain a composition formula of Na _x Ni _Y Mn _{1 -YO 2} (provided that , 0 <x <1, 0 <y <1). On the other hand, Li-bromide or Li-chloride is dissolved in n-hexanol in a nitrogen stream to obtain a concentration of 0.05 to 5 mol / l. A Li bromide solution or a Li chloride solution is prepared, and the composition formula is Na _x Ni _Y Mn _{1-YO 2} (where 0 <
x <1, 0 <y <1) with the compound represented by Li bromide
The composition formula is Na _x Li ₁ , which is added to the solution or the Li chloride solution so as to satisfy 4 ≦ Li / Na ≦ 20, and is stirred and reacted in a nitrogen stream while maintaining the temperature at 135 to 145 ° C. _-x Ni _Y Mn _{1-YO 2} (where 0 <x
A method for producing a positive electrode active material for a lithium secondary battery, comprising a compound represented by <1, 0 <y <1) and having a monoclinic crystal structure. 10. An oxide of sodium carbonate, manganese oxide, and Cu is compounded, mixed, molded, and fired to obtain a composition formula of Na _x Cu _Y Mn ₁ -YO ₂ (where 0 <x <
1, 0 <y <1) is prepared, and Li bromide or Li chloride is dissolved in n-hexanol in a nitrogen stream to obtain a Li bromide solution having a concentration of 0.05 to 5 mol / l or A Li chloride solution was prepared, and the composition formula was Na _x Cu _Y Mn _{1-YO 2} (where 0 <
x <1, 0 <y <1) with the compound represented by Li bromide
The composition formula is Na _x Li ₁ , which is added to the solution or the Li chloride solution so as to satisfy 4 ≦ Li / Na ≦ 20, and is stirred and reacted in a nitrogen stream while maintaining the temperature at 135 to 145 ° C. _-x Cu _Y Mn _{1-YO 2} (where 0 <x
A method for producing a positive electrode active material for a lithium secondary battery, comprising a compound represented by <1, 0 <y <1) and having a monoclinic crystal structure.