JP4362355B2 - Positive electrode material powder for lithium secondary battery and lithium secondary battery - Google Patents

Description

The present invention relates to a positive electrode material Powder及 beauty lithium secondary battery for a lithium secondary battery, and more particularly, to improvements in addition to the positive electrode material for a lithium secondary battery having a composition of Li-Ni-Co-Ba- O -based were novel wood charge及 beauty lithium secondary battery using the novel material.

  In recent years, various improvements have been made in the positive electrode material for lithium secondary batteries, and a Li-Ni-Co-O-based or Li-Ni-Co-Ba-O-based composition has been used as a positive electrode material for high-capacity secondary batteries. There are materials to have.

As an example, there is a positive electrode active material which is a compound represented by the chemical formula Li _{1 -Xa} A _X Ni _{1 -Yb} B _Y O.

However, A: at least two alkaline earth metal elements selected from strontium or barium or magnesium, calcium, strontium and barium B: at least one transition metal element excluding Ni X: total of A Represents the number of moles, 0 <X ≦ 0.10
Y: represents the total number of moles of B, 0 <Y ≦ 0.30
a: −0.10 ≦ a ≦ 0.10
b: −0.15 ≦ b ≦ 0.15
(For example, see Patent Document 1).

Further, a positive electrode active material comprising a compound represented by formula _{Li 1-Xa A X Ni 1} -Yb B Y O, and positive electrode active material average particle diameter of 0.01μm or more, or less 5.0μm There is a positive electrode active material that forms secondary particles that are aggregates of primary particles, and the average particle diameter of the secondary particles is 5.0 μm or more and 50 μm or less.

However,
A: Strontium or barium B: At least one transition metal element X: X is the total number of moles of strontium or barium, 0 <X ≦ 0.10
Y: Total number of moles of all transition metal elements other than Ni 0 <Y ≦ 0.30
a: −0.10 ≦ a ≦ 0.10
b: −0.15 ≦ b ≦ 0.15
(For example, refer to Patent Document 2).

  These materials have excellent cycle characteristics when used for a positive electrode for a lithium secondary battery, but do not mention thermal stability, capacity, rate characteristics, and charge / discharge efficiency.

The present inventors proceeded with research on a positive electrode material for a lithium secondary battery, and further studied the Ba content with respect to the same Li—Ni—Co—Ba—O-based technology as in the above technology, and the Ba content. In this narrow range, a material having high thermal stability and large capacity has been proposed (for example, see Patent Document 3).
JP-A-9-17430 (page 2-8) JP-A-10-79250 (pages 2-7) Application for Japanese Patent Application No. 2001-173285 (page 3-11)

  As a result of diligent research on improving the characteristics of the positive electrode material for lithium secondary batteries, the present inventors have further developed a material having excellent characteristics as well as safety.

The present invention aims to provide such excellent performance positive electrode material Powder及 beauty lithium secondary battery novel lithium secondary battery having a.

The present invention is a powder of complex oxide entire composition represented by _{Li a Ni b Co c Ba d} M e O x, and lithium secondary batteries powder particles, characterized in that an oxide amorphous phase It is a positive electrode material powder for use.
However,
M: one or more selected from the group consisting of Na, K, Si, B, P and Al
element
a / (b + c): 0.9 to 1.1
b / (b + c): 0.5-0.95
c / (b + c): 0.05 to 0.5
d / (b + c): 0.0005 to 0.01
e / (b + c): less than 0.01 (excluding 0)
b + c = 1
x is not specified
It is.

  The positive electrode material powder for a lithium secondary battery of the present invention may be one in which the particles have the oxide amorphous phase dispersed therein, and the particles have the oxide amorphous phase on the surface thereof. It may be dispersed in. Furthermore, the particles may have the oxide amorphous phase dispersed inside thereof and on the surface thereof.

  Furthermore, the constituent component of the oxide amorphous phase is composed of an oxide of one or more elements selected from the group consisting of Li, Na, K, Si, Ba, B, P and Al. It is preferable for forming an oxide amorphous phase.

Furthermore, when comprehensive positive electrode material for a lithium secondary battery of the present invention, the overall composition _{Li a Ni b Co c Ba d} M e O x positive electrode for a lithium secondary battery which is a composite oxide represented by Material.
However,
M: one selected from the group consisting of Na, K, Si, B, P and Al, or
Two or more elements a / (b + c): 0.9 to 1.1
b / (b + c): 0.5-0.95
c / (b + c): 0.05 to 0.5
d / (b + c): 0.0005 to 0.01
e / (b + c): less than 0.01 (excluding 0)
b + c = 1
x is not particularly defined.

Positive electrode material for a lithium secondary battery described above, can be prepared by the following ways.

(1 ) An oxide composed of one or more elements selected from the group consisting of Li, Na, K, Si, Ba, B, P and Al as a Li— Ni—Co—Ba—O-based raw material Components for forming an amorphous phase are mixed and fired. Thus, a positive electrode material for a lithium secondary battery in which an oxide amorphous phase is dispersed inside the powder can be produced.

(2 ) A Li— Ni—Co—Ba—O-based material is fired, and the fired powder is subjected to one or two selected from the group consisting of Li, Na, K, Si, Ba, B, P, and Al. A component comprising an element of more than seeds and forming an oxide amorphous phase is added and baked again. This makes it possible to produce a positive electrode material for a lithium secondary battery having an oxide amorphous phase on the surface of the particles.

(3 ) An oxide composed of one or more elements selected from the group consisting of Li, Na, K, Si, Ba, B, P and Al as a Li— Ni—Co—Ba—O-based raw material After mixing the component which forms an amorphous phase, this is baked, and further from one or more elements selected from the group consisting of Li, Na, K, Si, Ba, B, P and Al. The components that form the oxide amorphous phase are mixed and fired again. This makes it possible to produce a positive electrode material for a lithium secondary battery in which an oxide amorphous phase is dispersed inside the particles and the surface of the particles also has an oxide amorphous phase.

  In addition, this invention provides the lithium secondary battery characterized by including the positive electrode comprised from the positive electrode material for lithium secondary batteries in any one of the above.

  According to the present invention, a positive electrode material for a lithium secondary battery having high safety, large capacity, excellent cycle characteristics and rate characteristics, and high charge / discharge efficiency can be obtained.

The present invention is a positive electrode material powder for a lithium secondary battery mainly comprising a Li- Ni-Co-Ba-O-based component, wherein the particles constituting the powder have an oxide amorphous phase. And

here,
(A) An oxide amorphous phase is dispersed inside the particle. (B) An oxide amorphous phase is formed on the surface of the particle. (C) An oxide non-phase is formed inside the particle and on the particle surface. A crystalline phase may be formed.

Although the action of the oxide amorphous phase is not necessarily clear, it improves the charge / discharge capacity and charge / discharge efficiency because it improves the permeability of the electrolyte. Further, it is possible to improve the cycle characteristics by preventing collapse of the positive electrode material even when expansion and contraction of the charging and discharging that by the Li -Ni-Co-Ba-O-based composite oxide crystal. Furthermore, it is effective in preventing gelation and improving electrode density in the electrode manufacturing process.

Oxide amorphous phase-forming elements such as Li, Na, K, Si, Ba, B, P, and Al do not necessarily have to be added in their entirety as oxide amorphous phase products. May be contained in the Li- Ni-Co-Ba-O-based crystal.

  The composition of the oxide amorphous phase is one or more elements selected from the group consisting of Li, Na, K, Si, Ba, B, P, and Al. There are other elements forming the glass phase (for example, Ca, Mg, Zn, Ti, Sr, Zr, S, Fe, Ge, As, W, Mo, Te, F, etc.), Li to Al Other elements may be contained in the amorphous oxide containing one or more elements selected from the group consisting of:

  The reason for the numerical limitation will be described below.

The present invention is obtained by adding the improvement to the positive electrode material powder for a lithium secondary battery mainly comprising that have been known Li -Ni-Co-Ba-O system component.

Note that the following numbers, the sum of Ni and Co when the overall composition expressed as _{Li a Ni b Co c Ba d} M e O x of a positive electrode material for a lithium secondary battery which composite oxide of the present invention is 1 This represents the number of moles of each component when moles (that is, b + c = 1).

  Li is 0.9 to 1.1 mol. When there is little Li, it will become a crystal structure with many lithium vacancies, and capacity | capacitance will fall. If the amount is too large, hydrates and carbonates are formed, and a gelled state is produced during electrode production.

  Co increases the thermal stability, but if it is too much, the discharge capacity is reduced, so Co is 0.05 to 0.5 mol.

  Ba contains 0.0005 to 0.01 mol in order to improve thermal stability. When the content is more than 0.01 mol, the discharge capacity is lowered.

  The oxide amorphous phase is less than 0.01 mol. However, zero is not included. If it is 0.01 mol or more, the discharge capacity is mainly reduced, so it is desirable to make it less than 0.01 mol. The oxide amorphous phase must be present inside or on the surface of the material powder of the present invention. Therefore, it does not include zero.

An oxide amorphous material composed of one or more elements selected from the group consisting of Li, Na, K, Si, Ba, B, P and Al as a Li— Ni—Co—Ba—O-based material A positive electrode material for a lithium secondary battery having an oxide amorphous phase inside the particles can be produced by mixing less than 0.01 mol of a component forming a phase and firing the mixture. The produced oxide amorphous phase is scattered in the particles of the Li— Ni—Co—Ba—O-based material.

Moreover , the Li— Ni—Co—Ba—O-based raw material was fired and crushed, and the crushed powder was selected from the group consisting of Li, Na, K, Si, Ba, B, P, and Al. By adding a small amount of less than 0.01 mol of a component composed of one or more elements to form an oxide amorphous phase, and firing again, the oxide amorphous phase is dotted on the surface of the particles. The positive electrode material for lithium secondary batteries which is scattered and adhered can be manufactured.

  Next, examples of the present invention will be described.

Ni—Co— (OH) ₂ suitable as a raw material for the Ni source and the Co source is adjusted such that the ratio of Co to the total amount of Ni and Co is 0.05 to 0.5 in terms of molar ratio. In the production, a fine secondary powder of Ni—Co— (OH) ₂ is produced, for example, by a wet synthesis method. In this case, the average particle diameter is 5 to 20 μm and the tap density is 1. It is desirable to adjust so that it may become 8 g / cm < ³ > or more. In general, when a lithium composite oxide is synthesized, the shape and density of Ni—Co— (OH) ₂ as a starting material are reflected.

  As a raw material for forming an oxide amorphous phase composed of one or more of Li, Na, K, Si, Ba, B, P, and Al, an oxide or a material that becomes an oxide by firing can be applied. .

Since the nitrates of Li, Na, K, and Ba are highly reactive at the time of firing and assist the formation of an amorphous phase and have a strong oxidizing power, the main Li— Ni—Co—Ba—O-based positive electrode Although it is suitable at the point which gives an active characteristic to a material easily, it is not limited to this.

As for Si and Al, amorphous fine particles having a BET specific surface area of 100 m ² / g or more are suitable, but are not limited thereto.

  An oxide amorphous phase composed of one or more of Li, Na, K, Si, Ba, B, P, and Al functions effectively in order to obtain performance as the positive electrode material powder of the present invention.

  In order to form this oxide amorphous phase, the above-mentioned raw materials can be used. Alternatively, it is also possible to use glass powder once produced and pulverized.

Moreover, when synthesizing Ni—Co— (OH) ₂ , one or more of Li to Al may be added.

The kinds of oxides amorphous phase to form, the firing temperature is appropriately selected is but an oxidizing atmosphere of 900 ° C. or less so as not to degrade the contributing properties of Li -Ni-Co-Ba-O-based material as a main component Preferably there is.

(Examples 1-10, 17-19)
As a raw material Ni source and Co source, three types of Ni—Co— (OH) ₂ , which can be adjusted to molar ratios of Co / (Ni + Co) = 0.1, 0.2, and 0.3, respectively, are prepared by wet solution synthesis. It was produced by.

Other starting materials used were commercially available chemicals. Respectively,
Li source is LiOH.H ₂ O
NaNO ₃ is used for Na source
KNO _{3 for} K source
The Ba source has Ba (NO ₃ ) ₂
B source is H ₃ BO ₃
Al source contains Al ₂ O ₃
For Si source, SiO ₂
The P source contains P ₂ O ₅
Was used. Incidentally, amorphous fine particles were used for Al ₂ O ₃ and SiO ₂ .

  These starting materials were selected and weighed so as to obtain the desired blend composition, and then sufficiently mixed to obtain a raw material for firing. Firing is carried out in an oxygen atmosphere, first held at 400 ° C. for 4 hours, mainly removing moisture in the raw material, then holding the firing temperature and time shown in Table 1 at a heating rate of 5 ° C./min, after cooling, The fired product was taken out from the furnace.

  The taken fired product was crushed to obtain a positive electrode material powder. The obtained powder was subjected to particle size distribution measurement and chemical analysis by a laser diffraction method. From the chemical analysis values, the molar ratio of each element to Ni + Co = 1 and the average particle size by particle size distribution measurement are shown in Table 1.

  Next, Table 2 shows the results of trial manufacture of a lithium secondary battery and evaluation of the battery characteristics of the positive electrode material.

(Comparative Examples 1-3)
Except for the change of the blending composition, the types of raw materials and firing were performed in the same manner as in the examples.

  Tables 1 and 2 show the components and battery characteristics as in the examples.

  The evaluation method of battery characteristics is shown below.

N-methyl-2-monopyrrolidone was added to 90% by mass of the positive electrode material powder for lithium secondary batteries obtained in Examples and Comparative Examples, 5% by mass of acetylene black and 5% by mass of polyvinylidene fluoride, and after kneading, 20 μm A thick aluminum current collector applied and dried was pressed with a roll-type press to a thickness of 80 μm, and punched to a diameter of 14 mm, and vacuum dried at 150 ° C. for 15 hours to obtain a positive electrode. A lithium metal sheet was used as the negative electrode material, and a polypropylene porous membrane was used as the separator. As the electrolytic solution, 1 mol of LiPF ₆ dissolved in 1 liter of a mixed solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) in a volume ratio of 1: 1 was used. The test cell was assembled in a glove box substituted with argon. The charge capacity and the discharge capacity were determined between 3.0 and 4.2 V at a constant current density of 1.0 mA / cm ² . Furthermore, the first charge / discharge efficiency was calculated by the following formula.

Initial charge / discharge efficiency = (initial discharge capacity) / (initial charge capacity) × 100
In the measurement of rate characteristics, charge / discharge measurement was further performed at 3.0 to 4.2 V at a constant current density of 5.0 mA / cm ² , and calculation was performed using the following formula.

Rate characteristic (%) = {(discharge capacity value at 5.0 mA / cm ² )
/ (Discharge capacity value at 1.0 mA / cm ² )} × 100
The cycle characteristics were assembled in the same test cell, charge / discharge measurements were repeated between 3.0 and 4.2 V at a constant current density of 5.0 mA / cm ² , measured up to 100 cycles, and calculated by the following formula.

Cycle characteristics (%) = {(discharge capacity value at 100th cycle)
/ (Discharge capacity value at the first cycle)} × 100
A battery for nail cutting test was made as follows.

After mixing 89% by mass of the positive electrode material powder for lithium secondary battery synthesized in Example 3, 6% by mass of acetylene black and 5% by mass of polyvinylidene fluoride, adding N-methyl-2-pyrrolidone and kneading sufficiently. The positive electrode was produced by applying, drying and pressing an aluminum current collector with a thickness of 20 μm. For the negative electrode, N-methyl-2-pyrrolidone was added to 92% by mass of carbon black, 3% by mass of acetylene black, and 5% by mass of polyvinylidene fluoride, kneaded and then coated, dried and applied with a 14 μm thick copper current collector. It was made by pressing. The electrode thicknesses of the positive electrode and the negative electrode were 75 μm and 100 μm, respectively. The electrolyte is a solution of 1 mol of LiPF ₆ in 1 liter of a 1: 1 mixed solution of ethylene carbonate (EC) / methyl ethyl carbonate (MEC). The separator is a polypropylene porous membrane and an aluminum laminate. A square battery having dimensions of 60 mm × 35 mm × thickness 4 mm was made as a prototype. As a result of charging to 4.2 V with a current value of 160 mA and measuring the discharge capacity to 3.0 V with the same current value, it was 800 mAh.

  Batteries were produced in the same manner for the positive electrode material powders for lithium secondary batteries synthesized in Examples 6, 9, 11, 14, 16 and 17 and Comparative Examples 1 to 3. In the nail cutting test, the battery was charged at a constant current / constant voltage up to 4.2 V at a current value of 160 mA for 8 hours, and then a nail having a diameter of 2.5 mm was penetrated through the center of the battery at a speed of 15 mm / sec. The state of the battery was observed. If there was no smoke, fire, or rupture, the test was accepted. If smoke, fire, etc. were observed, the test was rejected.

(Examples 11 to 16)
The initial product was obtained by the raw materials used in Examples 1 to 10 and the same firing method. Additive components shown in Table 3 were added to the initial product, fired again in an oxygen atmosphere, and pulverized to obtain a positive electrode material powder. Examples 11, 13, 14 and 15 are those in which an oxide amorphous phase is formed on the surface of the particles, and Examples 12 and 16 are those in which an oxide amorphous phase is formed on the particles, the surface and inside. is there. Table 3 shows the average particle diameter by laser diffraction and the molar ratio of each element from chemical analysis. Further, a lithium secondary battery was prototyped from these, and the battery characteristics of the positive electrode material were evaluated and are shown in Table 4. The examples of the present invention have a large discharge capacity, high charge / discharge efficiency, excellent rate characteristics and cycle characteristics, and pass test results.

Claims (5)

Overall composition is a powder of composite oxide represented by _{Li a Ni b Co c Ba d} M e O x, and
A positive electrode material powder for a lithium secondary battery, wherein the powder particles have an oxide amorphous phase.
However,
M: one or more selected from the group consisting of Na, K, Si, B, P and Al
element
a / (b + c): 0.9 to 1.1
b / (b + c): 0.5-0.95
c / (b + c): 0.05 to 0.5
d / (b + c): 0.0005 to 0.01
e / (b + c): less than 0.01 (excluding 0)
b + c = 1
x is not specified
It is.   The positive electrode material powder for a lithium secondary battery according to claim 1, wherein the particles have the oxide amorphous phase dispersed therein.   The positive electrode material powder for a lithium secondary battery according to claim 1, wherein the particles have the oxide amorphous phase dispersed on the surface thereof.   2. The positive electrode material powder for a lithium secondary battery according to claim 1, wherein the particles have the oxide amorphous phase dispersed therein and on the surface thereof. 3.   A lithium secondary battery comprising a positive electrode comprising the positive electrode material for a lithium secondary battery according to claim 1.