JPH03219571A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To improve the cycle characteristics and obtain a sufficient discharge capacity after a cycle by using a negative pole of lithium and positive pole active material expressed by a predetermined expression. CONSTITUTION:A positive pole 1 is put in a case 2, a separator 3 is put on the positive pole 1, a negative pole of a lithium plate 4 is pressure-applied to an enclosing plate 5 having a gasket 6, and mixed solution including lithium salt is added to the separator 3 and the negative pole. Positive pole active material expressed by an expression LixMyMn(2-y)O4, where M refers to at least one material consisting of Co, Cr, Fe, with 0.85<=x<=1.15 and 0.02<=y<=0.3, is used for the positive pole 1. Lithium is removed from the positive pole active material by changing, so the composition of the positive pole active material becomes LixMyMn(2-y)O4 (X<=0.7) when a battery is charged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the improvement of non-aqueous electrolyte secondary batteries, particularly to the improvement of positive electrode active materials, and is aimed at improving the cycle characteristics of batteries.

Conventional technology Non-aqueous electrolyte secondary batteries using lithium or lithium compounds as the negative electrode are expected to have high voltage and high energy density, and although many studies have been conducted, patents such as M n O2 and T
i5a is being widely considered. Recently, Takley et al. reported that LiMnaQs can be used as a positive electrode active material (Material Research Bulletin 1983, Vol. 18, 4).
(pages 61-472). LiMn2O4 has a cubic crystal structure with a spinel structure, and when used as a positive electrode active material of a battery, the discharge voltage of the battery is as high as about 4 volts, and it is considered to be a promising positive electrode active material.

However, this positive electrode active material had a problem with its cycle characteristics.In other words, when charging and discharging were repeated, the discharge capacity decreased significantly. As shown in Figure 2, there are two discharge curves, one near 4 volts and one near 2.8 volts.

The horizontal axis shows the composition of the positive electrode active material at this time. Charging and discharging occur due to the entry and exit of Ll into the positive electrode active material. If the composition of the active material is not expressed as Li)1Mn204, charging and discharging occur due to changes in the value of X.

Until now, we have focused on the second stage of discharge near 2.8 volts, limiting the charging voltage to 3.8 volts and discharging to 2 volts, that is, charging and discharging in which X changes from approximately 1 to 1°85. Good cycle characteristics are obtained.

However, with this (t) high energy density cannot be achieved (t
To achieve high energy density, the first stage of discharge is to charge to +14.5 volts and discharge to 3 volts, that is, charge until X becomes 1 or less, preferably 0.7 or less, or until LX becomes 1 or +i1.85. It is more advantageous to discharge until the However, the cycle characteristics of the first stage of charging and discharging, which charges until X becomes 0.7 or less, are poor, and the discharge capacity drops to half after about 50 cycles. If the battery is charged to such an extent that X exceeds 0.7, the charging is insufficient and it is difficult to obtain sufficient discharge capacity.

Problems to be Solved by the Invention The present invention aims at improving the cycle characteristics of a non-aqueous electrolyte secondary battery using LiMnaO4 as a positive electrode active material.

Means for Solving the Problems In a nonaqueous electrolyte secondary battery in which lithium or a lithium compound is used as a negative electrode and a nonaqueous electrolyte containing a lithium salt is used as a positive electrode, the formula Li At least one type consisting of CrSFe, and 0.85≦X≦1.15, and 0
．． It is characterized by using a positive electrode active material in which 02≦Y≦0.3. Furthermore, lithium is extracted from the positive electrode active material by charging (compositional force of the positive electrode active material in the charged state <, L
It is characterized in that i yMvMn +2−v+oa (X≦0.7).

Effect LiMna04 has a cubic crystal structure with a spinel structure, and when charged, Ll is extracted from the crystal, and when discharged, Li enters the crystal. When LiMnaO4 was examined by X-ray diffraction after repeated charging and discharging cycles, it was found that the crystallinity had decreased! ,, When we chemically synthesized the active material by changing the value of X as L jj1MnaQ4 and examined its characteristics, we found that the discharge capacity and cycle characteristics changed depending on the value of X.
This indicates that the crystal stability of the active material itself is involved in the cycle characteristics.

There'? ', Mn in LixMn204 is partially co or C
As a result of examining active materials substituted with r and Fe, LiMn2
Compared to 0a, the crystal lattice constant is smaller.9 When these are used to investigate the characteristics as a positive electrode active material for secondary batteries, it is found that the positive electrode active material for secondary batteries has good cycle characteristics and has a large discharge capacity after cycling. I believe that the reason for this is that when LiMn20a is replaced with Fe or Cr, the lattice constant of the spinel structure becomes smaller, which increases the stability of the crystal and improves the cycle characteristics.

Example Examples will be described below.

<Example 1> As an active material in which Mn of Li2CO5 was replaced with Co, L
A method for producing LiMn20a using a solid solution of iMn2O4 and LiCoQa. A plate in which 3 moles of Li2CO5 and 4 moles of Mn304 were well mixed. The mixture was heated at 900°C in the air for 10 hours to produce LiMn2Q4.

Production method of LiCoO2 A plate in which Cocos was well mixed at a ratio of 2 moles to 1 mole of Li2CO5. Similarly, the mixture was heated to 900°C in the air.
Production method of LiMn2O4 with solid solution of LiCo0a LiCo
After thoroughly mixing LiMnaO4 at a ratio of 45 moles to 10 moles of O2, the mixture was heated in the air at 900°C for 40 hours to produce a battery.LiMna in which LiCo0a was dissolved as a positive electrode active material
7 parts by weight of O4, 2 parts by weight of acetylene black as a conductive agent, and 1 part by weight of polytetrafluoroethylene resin as a binder were mixed to prepare a positive electrode mixture. The positive electrode was press-molded to 5 mm at a rate of 1 ton/cmQ. A cross-sectional view of the manufactured battery is shown in FIG. Place the molded positive electrode 1 in the case 2. A porous polypropylene film was placed on the positive electrode 1 as a separator 3. A lithium plate 4 with a diameter of 17.5 mm and a thickness of 0.3 mm was placed as a negative electrode on the sealing plate 5 with a polypropylene gasket 6 attached. As a non-aqueous electrolyte. , using a mixed solution of propylene carbonate and dimethoxyethane in a volume ratio of 1:1 in which 1 mol/I of lithium perchlorate was dissolved.
Add this to the separator and negative electrode. Then seal the battery and call this battery A.

Similarly, a battery B uses LiMn2O4 as a positive electrode active material as a conventional example. Furthermore, as a conventional example, LiC
A battery using oO2 as a positive electrode active material is designated as C. Charge these batteries to 4.5 volts with a constant current of 2 mA.
Under these conditions of discharging to 3 volts and repeating this charging and discharging, in the first cycle, as shown in Figure 2, X, which indicates the composition of Li in the positive electrode active material, is 0.7 or less.
, charged until it reached 3, and discharged until X reached 1.

Figure 1 plots the discharge capacity of these batteries at each cycle. This shows that the LiMrz04 positive electrode containing LiCoO2 as a solid solution of the present invention shows little deterioration even after repeated charging and discharging cycles. In addition, Fig. 4 shows the discharge curves of each battery at the 10th cycle, where there is still little deterioration as a typical discharge characteristic.
It is discharged at the same potential as LiMngo4, and LiC
It can be seen that this is different from oO2. When LiMn2O4 in which LiCoO2 of this example was dissolved in solid solution was examined by X-ray diffraction, the diffraction pattern was the same as LlMn204.However, the peak position was shifted to the higher angle side compared to LiMnaO4, and it was determined from each diffraction peak. lattice constant I
8.21 people were smaller than 8.24 people for L LiMnaO4.9 The effect can be estimated from the results.
We believe that the smaller lattice constant makes the crystal more stable and improves cycle characteristics.

Generally spinel (AB204 like Dai LiCoO2)
It has a composition of Here, A +L is a metal light surrounded by an oxygen tetrahedron. 1Bli is a metal element surrounded by an oxygen octahedron. However, LLiCoOa does not have this composition (~
Therefore, it is believed that the solid solution described in this example has the composition as described below.

10LiCo02+45LiMnaO4= Lis
sCo +sM n s@Q 2111, that is, L
i +, +Co@, 2Mrz, eQ4, Co and M
A total of 2.0 min is surrounded by an octahedron of oxygen, and 1.0 min of hLi is surrounded by an octahedron of oxygen.
0 minutes is the same position as normal spinel, remaining 0.1
I think that the fraction will fit into the vacant oxygen tetrahedron in the spinel. As described above, LiMn2O41 in which LiC001+ of the present invention is dissolved in solid solution is a composition different from ordinary spinel.

<Example 2> In this example? tLiMn2O4 with various LiCoO2 dissolved in it by changing the ratio of LiCoOa and LiMn2Q4
In the same manner as described in Example 1, in which the characteristics of the positive electrode active material were investigated, a battery was manufactured by heating and its characteristics were investigated. The value obtained by subtracting the discharge capacity at the 50th cycle from the discharge capacity and dividing it by the discharge capacity at the 10th cycle is used.In other words, it is the deterioration rate due to board cycles, and the smaller this value is, the better it is. . Figure 5 shows LiC when creating a solid solution.

O+! The cycle characteristics of the active material are plotted against the ratio of LiMn2O4 and LiMn2O4. LiC002
However, the degree of improvement slows down from around 10:45 when the ratio of LiMn2O4 to LiMn2O4 increases.

Q-10- Furthermore, the ratio of LiCoO2 increased is 50:25 (in fact, the cycle characteristics deteriorate.

From this, it is better to have a ratio of LiCo0e to LiCo0e of 2:49 to 30:35, especially 5:47゜5 to 26.
It can be seen that vs. 37 is desirable.

In other words, expressed in terms of the composition of the solid solution, L i +, s + Co
s.

eaMnll, 5eQ4 to L i +, +sCo @
, sM n @, 704 is good, especially L i +, 5a
sCo @, ll5M n @, eso s to Li+
, +sc oll, 2aMns, vzoa is desirable l,
% When the active material used in this example was examined by X-ray diffraction, Li
Solid solutions of CoO2 and LiMn2O4 with a ratio of up to 30:35 show the same diffraction pattern as LiCo0a, and LiC
It was found that as the ratio of solid solution of o0a increases, the lattice constant of the cubic crystal becomes smaller.If the ratio is higher than this, other peaks appear in the diffraction pattern, making it difficult to say that it is only a cubic crystal.

<Example 3> In Examples 1 and 2, LiM containing LLiCoOa as a solid solution
LiCoQt and Li2CO are used to produce n*04.
3 was reacted. In this method, f & LicoOp and LiM
In this example, i;
t-, instead of producing LiCoOs and LiMn2O4 separately, a predetermined amount of Li2CO3, Mn30a, and CoCO8 were thoroughly mixed, and then heated at 900°C for 10 hours to react, as described in Example 1. 27.5 mol of QLi2CO* and 3 mol of M n s O4 to produce a solid solution with the composition
After mixing CoCO3 in a ratio of 0 mole and 10 mole,
The same results were obtained when the product was heated at 900°C for 10 hours and subjected to X-ray diffraction and similar battery tests (Example 4).
By dissolving LiCoO2 in n2O4, L
It was discovered that the cycle characteristics of batteries could be improved while retaining the crystal structure of iMn2O4.
It enters in the form of substituting Mn, and as for Li, oxygen 4
It is considered that the increase is more than 1.

11 2-Example 3 l:L LixCovMn+2-v+oa
It turns out that Li compounds and Co compounds can be synthesized by mixing a predetermined amount of Mn compounds and heating them. Then, we fixed X and changed the value of Y for LixCoYMnte-v)04 (7), Fix Y and set X
The cycle characteristics of the positive electrode active material were investigated by making products with different values of X = 1.0, 1.01, 1.025, 1.05, 1゜1
Y=0, 0 for 0, 1.15, 1.20, respectively
,01,0.02,0.05,0.1,0.2.0.3
, 0.4 Li2COa, CoCO3, M
Weigh n5Oa and prepare a solid solution in the same manner as in Example 3,
Prototype a battery as in Example 1, conduct a cycle test, and take the deterioration rate as the cycle characteristic as in Example 2. Table 1 shows the deterioration rate of the active material corresponding to each of X and Y. From this, it was found that both the amount of Li in ζiX and the amount of Co in Y are effective in improving the cycle characteristics of the positive electrode active material.However, if too much L13-1≠-1 and Co are used, the effect becomes ineffective. It is also clear that from Example 1 to Example 4, L i XCOVM n 1
24) When the amount of Co, which is Y in 04, is 0.02 or more and 0.3 or less, X as Lift is 1 or more and 1.15 or less, and the cycle characteristics are good.Therefore, the non-aqueous electrolyte has a large discharge capacity after cycling. A secondary battery is obtained.

<Example 5> Next, L i XCOYM n +2-y+o a's X
is smaller than 1. LiMn2O4 production method carried out in the same manner as in Example 1. After mixing well, the mixture was heated in the air at 900℃ for 10 hours to prepare 9. Production method of i x COvM n 11!-vl Q a Using LiaCO3, MnaOz and Cocoa, Li
After mixing well in a ratio of X moles of Ay atoms, Y moles of Co atoms, and 2-Y moles of Mn atoms, the mixture was heated in the air at 900 ° C. for 10 hours to form a pond X = 0.95, 0.
Y=0.01 for each of 90, 0.85, 0.80
, 0.02, 0.05, 0.1.0.2, 0.3, 0.
4 was made as the positive electrode active material, and 9 batteries were manufactured and the charging/discharging test was conducted in the same manner as in Example 1. Under these conditions (in the first cycle, the composition of Li in the positive electrode active material was X shown is 0.7 or less
, 3. This means that the charging LX has been discharged to 1.

Figure 6 shows the discharge capacity of these batteries in the first cycle plotted against X of LiMn2O4.

From this, it can be seen that the smaller X is, the more the discharge capacity increases.

The 10th index represents the cycle characteristics of the positive electrode active material.
The value obtained by subtracting the discharge capacity of the 50th cycle from the discharge capacity of the 50th cycle and dividing it by the discharge capacity of the 10th cycle is used.In other words, this value is the deterioration rate due to slope cycles. The smaller the better. Figure 7! '& The deterioration rate due to this cycle is plotted against X of Li-MneO4. As X becomes smaller, the deterioration rate increases.Therefore, as a positive electrode active material, LiMn2O4 in which part of the Mn was replaced with co, Li xCo vM n (2-v
A battery was constructed in the same manner as described above using ROS, and a charge/discharge test was conducted. discharge capacity of mA
Table 3 shows the deterioration rate of each active material due to cycles.
The discharge curves at the 50th cycle of the battery using @, +Mns, sQ4 and the conventional battery B using LiMn2O4 are shown.k It can be seen that the battery of this example is superior.

Table 2 Table 3 Table 7- From the above, L i x COvM n 1-yl Q
When Y of a is 0°02 or more and 0.3 or less, the cycle characteristics improve, and when X is less than 1 and 0.85 or more, l&
The discharge capacity is also larger than that of Li, 1MnaO4~ When LixCovMrz2-ν104 of the present invention was examined by X-ray diffraction, the diffraction pattern was the same as that of LiMn2Q4.However, the position of the peak was shifted to the higher angle side compared to LIMnaQ4. The lattice constant determined from each diffraction peak (for example, 8.21 people for LiMn2Q4 was smaller than 8.24 people for LiMn2Q4). We believe that this is because the crystal has become more stable and the cycle characteristics have improved.

From Example 5, expressed by the formula L i XCovMn + ay + Q4 h
o.

By using a material satisfying 85≦X<1 and 0.02≦Y≦0.3 as the positive electrode active material, the capacity of the nonaqueous electrolyte secondary battery can be increased and the cycle characteristics can be improved.

Combining the above Examples 1 to 5, the formula Lix=19- Co vM n (2-Y> expressed by Oa h O,8
By using a material satisfying 5≦X<1°15 and 0.02≦Y≦0.3 as the positive electrode active material, the capacity of the nonaqueous electrolyte secondary battery can be increased and the cycle characteristics can be improved.

Next It; Mn in LiMn2O4 is partially replaced by Cr or Fe.
It was found that the discharge capacity decreased slightly only in the first cycle, but it became a secondary battery-like positive electrode active material with good cycle characteristics, and after the 5th cycle, the discharge capacity also decreased. I think the reason for this is that when Mn in LiMn2O4 is replaced with Fe or Cr, the lattice constant of the spinel structure becomes smaller, as in the case of co, which increases the stability of the crystal and improves the cycle characteristics.

Further to ζ It was found that the cycle characteristics of LiMn2O4, in which a part of Mn was replaced with Fe or Cr at the stage of chemical synthesis, is further improved as X becomes more than 1 (Example 6) Li MvMnta −, +O−(M=Cr, F
Production method of e) - Addition - LiaCOs, Mrz04 and CraOa and 1, t, F
After mixing well using e2O3 in a ratio of 1 mole of L11 or less, 2 moles of Cr atoms or Fe atoms (Y mole), and 2-Y moles of Mn atoms, the mixture was heated in the air at 900 ° C. for 10 hours. Y=0 as Cr or Fe made by heating.
01.0.02.0.05.0゜1.0.2, 0.3,
0.4 was made and used as the positive electrode active material.Battery manufacturing and charge/discharge tests were conducted in the same manner as in Example 1 under these conditions (In the first cycle, Ll in the positive electrode active material was X indicating the composition of is 0.7 or less
, the battery was charged until it reached 3. This means that the battery was discharged for up to X months.

FIG. 9 shows L i Fes, 2, which is an example of the present invention.
Battery E using MH1, @04 and conventional LiMn
Looking at the charging curve corresponding to discharge, which shows the charging and discharging curve at the 100th cycle of battery B using 2O4, it can be seen that a charging voltage of 4 volts or more is required. In addition, the amount of electricity charged and the amount of discharged electricity according to the present invention are both better, as shown in Figure 1O! It can be seen that the cycle characteristics are better in the case of the example in which the discharge capacity of these batteries at each cycle is plotted.

After the completion of charging in the 101st cycle, a chemical analysis of the positive electrode active material was carried out, and the results showed that although X was 0°84, that of the present invention was 0°56.
It has been found that deterioration due to cycling is due to the fact that the cathode active material cannot be charged due to the collapse of crystallinity, 4, that is, it becomes difficult for Ll to escape from the active material.
The discharge capacity at the 50th cycle for each Y of , +Q4 is shown in mAH units. It can be seen that the battery is better.

From the above, it can be seen that when Y is 0.02 or more, the deterioration rate due to cycles becomes smaller. When Y exceeds 0.3, the rate of deterioration due to cycles increases. I think this is because strain occurs within the crystal.As a result, the discharge capacity decreases as shown in Figure 1121--ρ-9 From this,
The value of Y is 1, preferably 0.02 or more and 0.3 or less.Furthermore, using LiCrvMrz2-9)04 in which part of the Mn in iMnao4 is replaced with Cr, a battery is made in the same manner as described above. Configure it and perform a charge/discharge test.
In Fig. 13, It,, L i Cr vM n
i! ! -tll O4 shows the deterioration rate due to cycles of batteries using active materials of each Y. t-o L ] Cr v
Even when M n f2-ul Os is used as an active material, L
Similar to when using iFevMn(2-v)oa, Y was preferably 0.02 or more and 0.3 or less <Example 7> Chemically synthesized L i XMVM n (e-, +
Consider the influence of the value of X in Q4 on the cycle characteristics.Liy+MvMrxe-vroa (M=Cr,
F e) Preparation method Li2CO5, M n s O4 and Cr2bs also l&
Using Fep Q 3, the Li atom content is Xmo) Lt, Cr
Protoatomic property or Fe protoatomic trace Y mole, Mn atom content is 2-Y
The mixture was heated in the atmosphere at 900°C for 10 hours to make 9 Cr and Fe (Y = 0.0.01.0.02.0.05.0. 1,
X=1.0.1.01 for 0.2, 0.3, 0.4
, 1.025, 1.05, 1.10, 1.15.1.2
Test method for battery configuration with 0 as in Example 1. Deterioration rate was taken as in Example 6 as the cycle characteristic, and the deterioration of the active material corresponding to each X1Y when Fe was used as M. The ratio is shown in Table 4. From this, it was found that both the amount of Ll in X and the amount of Fe in Y are effective in improving the cycle characteristics of the positive electrode active material. The same deterioration in cycle characteristics as shown in Example 1 occurred when the Fe content was 0.02 or more and 0.3 or less.
It is considered that the Li content is preferably 1 or more and 1.15 or less.

Similarly, when Cr is used as Ex M, the same results as with Fe are obtained, and whereas the Cr content is 0.02 or more and 0°3 or less, the Li content is 1 or more and 1.15 or less. 24- From Examples 6 and 7 above, in a non-aqueous electrolyte secondary battery in which lithium or a lithium compound is used as a negative electrode and a non-aqueous electrolyte containing a lithium salt is used, the positive electrode E is at least one type consisting of Fe, and 1≦X≦1.
15 and 0.02≦Y≦0.3 t＼ Lithium is extracted from the positive electrode active material by charging (composition length of the positive electrode active material in the charged state L i XMVM n
By setting (2 + Oa (where X≦o, 7)), a lithium secondary battery with good cycle characteristics can be obtained.

Further (mi) As in Example 5, LixMvMn12-
Examining the case where X is smaller than 1 in Y2O2 (M: Fe, Cr) <Example 8> L 111M1+Mn+2-, +oi (M=Cr,
Fe) Production method Li2CO5, Mn5O4 and Cr2bsAl; LFe
208, the Li atoms are mixed in a ratio of 900 in the atmosphere
Y=O10,01,0,02 as 9Cr or l&Fe by heating at ℃ for 10 hours,
X for 0,05, 0,1, 0,2, 0,3, 0,4
= 0.95. Visually, as shown in Figure 2, X, which indicates the composition of Ll in the positive electrode active material, is 0.7 or less.
, charged until it reached 3, and discharged until X reached 1. When X exceeds 0°7 when charging is completed (
The discharge capacity is small and it is not practical as shown in Fig. 814 (Fig. 814).
e, aMrz, +) Battery F and L i s using O4,
ec r 9.2M1+, battery G using eQa and comparative example Li @ which has less Li and does not contain Fe or Cr
, battery H using eM n 20 s and conventional example L
The charging and discharging curve at the 50th cycle of battery B using iMn2O4 is shown, and when looking at the charging curve corresponding to round discharge, it is 4.
It can be seen that a charging voltage of volts or more is required. In addition, in Figure 15, the discharge capacity of these F, H, and B batteries is plotted in each cycle. It can be seen that the cycle characteristics become better when

Chemical analysis of the positive electrode active material after the completion of charging in the 101st cycle revealed that the positive electrode active material was of B in the conventional example (X was 0.58 in A of the present invention, although Y Ta
Figure 16 shows that deterioration due to cycling is due to the cathode active material becoming unable to be charged due to the collapse of crystallinity, that is, Li becoming difficult to escape from the active material.
The discharge capacity at the 50th cycle for each Y of Q4 is mA.
It can be seen that the battery of the present invention has a much superior discharge capacity compared to the conventional example in which the battery is expressed in units of H and has 9 Y=O.

As an index representing the cycle characteristics of the positive electrode active material, use the value obtained by subtracting the discharge capacity at the 50th cycle from the discharge capacity at the 10th cycle and dividing it by the discharge capacity at the 10th cycle. In other words, it is the deterioration rate due to the board cycle, and the smaller this value, the better.

FIG. 17 shows the deterioration rate of each active material due to cycles, and it can be seen that the battery of the present invention is superior to the conventional example where t and Y=0.

Similarly, L io, ec r vM n (e-v+o
The deterioration rate due to the cycle of the active material at each Y(7) of s is,
The X-ray diffraction shown in FIG. 18 shows that L i @, 9F e vM of this example.
n (e-v)04 and L i O,9Cr vM n
(When examining tv+Qa, the diffraction pattern is LiMna
Same as On, but the peak position is Li
It is believed that the lattice constant It, which was shifted to the higher angle side compared to Mn20n and determined from each diffraction peak, and the lattice constant, which was smaller than LiMnaQ4, became smaller, making the crystal stable and improving the cycle characteristics. .

From the above, it can be seen that when Y is 0.02 or more, the deterioration rate due to cycles becomes small. When Y exceeds 0.3, the rate of deterioration due to cycles increases. I think this is because strain occurs within the crystal. As a result, the discharge capacity becomes smaller as shown in FIG. 16.9 From this, the value of Y, Lt, 0.
02 or more and 0.3 or less is preferable.

Next, as a positive electrode active material, L j yF e vM n
L i XF e , M n (2-v+
0a(D each X.

Table 6 shows the discharge capacity at the 50th cycle for Y in mAH units.
Q s and +i Li XCr vM n (2-v
)04 when Y is 0.02 or more and 0.3 or less, the cycle characteristics are improved, and when X is less than 1 and 0.85 or more, (
Dai Complementary LiMn2Q conventional example and LiMn20n comparative example
The discharge capacity is also 5℃ thicker than that of L'x L I x
Cr yM n +2-v+Q a was also considered and Shima 141 30- Table 5 Table 6 Results Li) IF e vM n (2-v)
o Results with the same tendency as a were obtained when t-L and Y were 0.02
(5) When X is less than 0.3, the cycle characteristics improve;
The discharge capacity is also larger than a04 and comparative example L1xMn204.

Table 5 shows that even when Fe is included, the discharge capacity increases when X is less than 1 compared to X = 1 (as shown in Figure 6, when X is less than 1, the discharge capacity increases in the first cycle). This is thought to be the result of improved cycle characteristics due to the inclusion of Fe.

The circle or L indicates the result of charging to 4 or 5 volts, where X is 0.7 or less, and discharging until X becomes 1.
The present invention is not limited to discharging when X is up to 1, but is also effective when charging until X becomes 0.7 or less and discharging until LX becomes 1 or more and 1°8. This is because when charging and discharging when X is between 1 and 1.8, the composition of the conventional example also showed good cycle characteristics, and the positive electrode active material of this example also showed good cycle characteristics.

31 One Bird From Example 8, in a non-aqueous electrolyte secondary battery in which lithium or a lithium compound is used as a negative electrode and a non-aqueous electrolyte containing a lithium salt is used, the formula LixMYM H(a-v+
KM represented by Q4 is at least one of Cr and Fe, and 0.85≦X<1 and 0.02≦
By using a positive electrode active material in which Y≦0.3, a non-aqueous electrolyte secondary battery with good cycle characteristics can be obtained.

Combining Examples 6 to 8, in a nonaqueous electrolyte secondary battery using lithium or a lithium compound as a negative electrode and a nonaqueous electrolyte containing a lithium salt, the positive electrode
MvM n +2410 a, where M is Cr, F
at least one type consisting of e, and 0.85≦X≦
1.5 and 0.02≦Y≦0.3, a nonaqueous electrolyte secondary battery with good cycle characteristics can be obtained.

Furthermore, when Examples 1 to 8 are taken together, in a non-aqueous electrolyte secondary battery in which lithium or a lithium compound is used as a negative electrode and a non-aqueous electrolyte containing a lithium salt is used, the positive electrode ζζ is expressed by the formula Li XMYM n +e-v+ Oa.
is at least one of CO5Cr and Fe, and by using a positive electrode active material in which 0.85≦X≦1.5 and 0.02≦Y≦0.3, a non-aqueous electrolyte with good cycle characteristics can be obtained. You can get the next battery.

Until now (Table shows an example in which the discharge was stopped at 3V, the circle is only L) With the active material of the present invention, the discharge is deepened and the discharge is reduced to 2V as shown in Figure 2. In other words, not only the first stage discharge but also The cycle characteristics were good even after the second stage of discharge <Example 9> Charge/discharge test of batteries manufactured in the same manner using the same active materials as those described in Examples ① to 8. These batteries were charged to 4.5 volts with a constant current of 2 mA, discharged to 2 volts, and this charging and discharging process was repeated. This means that X, which indicates the composition of The active material exhibits good characteristics even when discharging up to 2 volts, as shown in Figure 19 (above).
1st cycle discharge curve (I-1) and 50th cycle discharge curve (I-50) of battery engineer using z, sQi
, and the discharge curve at the first cycle (Bl) and the discharge curve at the 50th cycle (B-50) of battery B using LiMnaO4, which is a conventional example. (-Comparing the discharge curves of the 1st cycle and the 50th cycle of battery B, the discharge time in the second stage of discharge of 3 volts or less and 2 volts or more is slightly shorter and some deterioration has occurred. However, the discharge time in the first stage part below 4.5 volts or more than 3 volts is considerably short and the deterioration is slow.In the battery I of the present invention (above), the second stage part of the discharge curve is almost No deterioration l,% Furthermore, it can be seen that there is little deterioration in the first stage.

This result indicates that the deterioration due to cycling occurs significantly in the first stage. It can be seen that the reason for the good characteristics was shown even in the case where the first stage deteriorated less.

<Example 10> Using the same active materials as in Examples 1 to 8 (＼ A battery was made in the same manner with only the electrolyte changed. LiCl0a, LiAsF5, LiPFe, Li each at 1 mol/l as solutes)
Using a lithium salt such as BFa 1. \As the solvent, use propylene carbonate, or a mixed solvent of propylene carbonate and ethylene carbonate at a volume ratio of 1:1.\These solutes and solvents are combined to form an electrolyte.The battery test is the same as in Example 1.The results are the same as in Example 1. Example 1
8, and the active material of the present invention exhibits good cycle characteristics (9). It shows.

<Example 11> - A. Using the same active materials as in Examples 1 to 8, a battery was made in the same manner with only the negative electrode changed. Using WO2 intercalated with Li-A1 and 4Li as the negative electrode. Battery test (same as Example 1 and Example 9. The results are almost the same as Example 1 and Example 9, and the active material of the present invention shows good cycle characteristics (Example 12) Using the same active materials as in Examples 1 to 8, batteries were made in the same manner as in Example 1, but were charged and discharged under the same conditions as in Example 1, with only the amount of charged electricity changed.By changing the amount of charged electricity, L was reached at the end of charging. i XMYM n +2-v+ Q4
The amount of X shown by changes. Therefore, the relationship between the amount of charge and the amount of discharged electricity was calculated by converting it into X at the end of charging and the amount of discharge per 1 g of active material. The relationship between the amount of charged electricity and the amount of discharged electricity in the first cycle of a battery using n+, aO4 is plotted according to the above. If it is below, there will be sufficient discharge capacity.

If the composition of the positive electrode active material in this charged state becomes XMO, 7 or less, sufficient discharge capacity will be obtained (the results are the same including the conventional example). To summarize the results, in a non-aqueous electrolyte secondary battery in which lithium or a lithium compound is used as a negative electrode and a non-aqueous electrolyte containing a lithium salt is used, the positive electrode is expressed by the formula: Li)1MvMn+2-I Q a 11. , M is at least one of Co, Cr, and Fe, and 0.85≦X≦1.15,
Use a positive electrode active material that satisfies 0.02≦Y≦0.3 ℃＼ Lithium is extracted from the positive electrode active material by charging, composition length of the positive electrode active material in the charged state Li xMvM n ce-v
+ Oa (however, X≦0.7) improves the cycle characteristics of the non-aqueous electrolyte secondary battery and provides sufficient discharge capacity even after the cycle has passed, which is of great industrial significance.

[Brief explanation of drawings]

Figure 1 shows the cycle characteristics of the battery Figure 2 shows 51Mn20
Figure 3 is a longitudinal cross-sectional view of the battery used in the test. Figure 4 is the discharge curve of the battery used in the test. Characteristic diagram Figure 5 is a characteristic diagram showing the deterioration rate of cycle characteristics with respect to the ratio of LiCo0a and LiMn2Q4.
Discharge capacity characteristic diagram in the first cycle with respect to X of Mn2Q4 Figure 7 is a characteristic diagram of cycle deterioration rate with respect to X of Li)1Mn204 Figure 8 is a diagram of Li) which is an example of the present invention
The discharge curves at the 50th cycle of the battery using LiMn2Q4, which is a conventional example, and the battery using LiMn2Q4, which is an example of the present invention, are shown in Figure 9. The discharge curves at the 100th cycle of Battery E using .2M n+, 8Qa and Battery B using LiMn2Q4, which is a conventional example, are as follows: Figure 10 shows the discharge capacity characteristics of the battery at each cycle. The discharge capacity characteristics at the 50th cycle for each Y of Li Fe vM n 1-u104 of the invention are shown in Figure 12.
LiFe vM n (2-v) which is the active material of the present invention
Deterioration rate characteristic diagram by cycle at each Y of 04 No. 13
The figure shows LiCr vM n (2-
Fig. 14 is a graph showing the deterioration rate characteristics due to cycles of batteries using active materials of each Y of v+ 04.
s, eF e 11.2M n +, battery F using eO4 and L i Il, ec r 9.2M n +,
Battery G using @04 and comparative example with less Ll and Fe
Figure 15 compares the charge-discharge curves at the 50th cycle of Battery H using Li @, @Mnao4, which does not contain Cr, and Battery B using LiMn2Qn, which is a conventional example. Characteristic diagram of discharge capacity Fig. 16 shows the L i s, eF e vM n (2-v)O of the present invention.
Discharge capacity characteristic diagram at the 50th cycle for each Y in 4.
Figure 17 HaruL i@, oFeyMnL2-v) oa Degradation rate poetry method by cycle at each Y Figure 18 is L
i e, oc r vMnl-yl Q a Fig. 19 shows the charging and discharging characteristics of the battery of the present invention and the conventional battery B at the 1st cycle and the 50th cycle. Curve Doctor Figure 20 is a diagram showing the relationship between the composition of the active material and the discharge capacity during charging. A: Battery of one embodiment of the present invention B: Conventional (FL
C, D, E, F, G, H, I... Batteries of different embodiments of the present invention 1... Correct! 2. Ke person 3. Separate Ku
439--40=...Lithium plate, 5...Sealing plate 6...Gasket.

Claims (2)

[Claims] (1) Lithium or a lithium compound as a negative electrode, a non-aqueous electrolyte containing a lithium salt, and Li_XM_YMn_(_2_-_Y_)O_4, where M is at least one of Co, Cr, and Fe, and 0.85 ≦X≦1.15, and 0.02≦
A non-aqueous electrolyte secondary battery characterized by using a positive electrode active material in which Y≦0.3. (2) The nonaqueous electrolyte secondary battery according to claim 1, wherein the composition of the positive electrode active material in a charged state is represented by Li_XM_YMn_(_2__Y_)O_4, and X≦0.7.