JP2003007303A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cycle characteristics under cool and high temperature environment. SOLUTION: In a nonaqueous electrolyte secondary battery 1 provided with a positive electrode 2 having a positive mixture layer 7 including a positive active material, a negative electrode 3 having a negative mixture layer 9 including a negative active material and a nonaqueous electrolyte, a polymer consisting of polymerized monomer molecules having a unit structure shown in a general formula 1 or 2, further preferably a polymer having a unit structure shown in a general formula 3, is added to the positive mixture layer 7. By the above-mentioned structure, in the positive electrode 2 added with the monomer molecules, the expansion and contraction are restrained when charging and discharging.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte including a positive electrode having a positive electrode mixture layer containing a positive electrode active material, a negative electrode having a negative electrode mixture layer containing a negative electrode active material, and a non-aqueous electrolyte. The present invention relates to a battery, and particularly to improvement of cycle characteristics at normal temperature and high temperature.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries, especially lithium ion secondary batteries, have a larger energy density and are lighter in weight than conventional lead-acid batteries, nickel cadmium batteries, etc., which are aqueous electrolyte secondary batteries. And has the advantage of high capacity.

A lithium ion battery having these advantages has been put to practical use as a driving power source for portable electronic equipment such as a mobile phone and a notebook personal computer, and has been widely used.

[0004]

A lithium ion battery is capable of inserting and extracting lithium and a positive electrode having a positive electrode active material layer containing a positive electrode active material such as a lithium composite oxide, a metal oxide or a metal sulfide. And a negative electrode having a negative electrode active material layer containing a negative electrode active material such as various materials.
Then, polyvinylidene fluoride (PV) is used as a binder in the positive electrode active material layer and the negative electrode active material layer of the lithium ion battery.
DF) and a styrene-butadiene-rubber polymer compound (SBR).

However, since the positive electrode active material and the negative electrode active material of the lithium ion battery expand and contract with the charge and discharge reaction, the positive electrode and the negative electrode also expand and contract in the lithium ion battery and contain the positive electrode active material. The binding strength between the positive electrode material mixture layer and the positive electrode current collector, and the binding strength between the negative electrode material mixture layer containing the negative electrode active material and the negative electrode current collector may decrease. As a result, there is a problem that the cycle characteristics of the lithium ion battery are deteriorated. Particularly, when the charge / discharge reaction is repeated in a high temperature environment, the positive electrode active material and the negative electrode active material are significantly expanded and contracted, so that the cycle characteristics are greatly deteriorated.

Further, it is known that polyvinylidene fluoride (PVDF) used as a binder swells slightly in a non-aqueous electrolytic solution, which easily leads to deterioration of cycle characteristics of a lithium ion battery. Furthermore, the styrene-butadiene-rubber polymer compound (SBR) may have insufficient adhesion to the current collector, which tends to deteriorate cycle characteristics.

In view of the conventional situation as described above, the present invention is
A non-aqueous electrolyte that is excellent not only in room temperature but also in cycle characteristics at high temperature by adding a new binder capable of suppressing expansion and contraction of the positive electrode and the negative electrode due to charge / discharge reaction to the positive electrode and / or the negative electrode. It was proposed for the purpose of providing a battery.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present invention have conducted extensive studies, and as a result, have found that a monomer unit containing a specific unit structure containing sulfur is used. When the combined material is added to the positive electrode and / or the negative electrode as a binder, expansion and contraction of the positive electrode and the negative electrode due to charge / discharge reaction can be suppressed,
It has been found that a non-aqueous electrolyte battery having excellent cycle characteristics not only at room temperature but also at high temperature can be realized.

The present invention has been completed based on such findings, and a positive electrode having a positive electrode mixture layer containing a positive electrode active material, a negative electrode having a negative electrode mixture layer containing a negative electrode active material, In a non-aqueous electrolyte battery including a non-aqueous electrolyte, a polymer obtained by polymerizing a monomer molecule having at least one of the unit structures shown in Chemical Formulas 4 and 5 below is the positive electrode mixture layer. And / or is added to the negative electrode mixture layer.

[0010]

[Chemical 4]

[0011]

[Chemical 5]

Although the clear reason why the non-aqueous electrolyte battery according to the present invention shows good results is not clear, the above polymer is a material that does not participate in the charge / discharge reaction of the non-aqueous electrolyte battery, and the polymer itself is not charged. Since it does not expand or contract as the discharge reaction progresses,
It is considered that the positive electrode and / or the negative electrode to which the polymer is added are suppressed in expansion and contraction due to the charge / discharge reaction, as compared with the positive electrode and / or the negative electrode to which the polymer is not added.

Further, since the above-mentioned polymer has high chemical resistance and is difficult to swell with a non-aqueous electrolytic solution or a non-aqueous solvent even at a relatively high temperature, the positive electrode and / or the negative electrode. Even when is expanded or contracted due to the charge / discharge reaction, the decrease in the binding strength between the current collector and the mixture layer is reduced.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A non-aqueous electrolyte battery to which the present invention is applied will be described below in detail with reference to the drawings.

The non-aqueous electrolyte battery 1 to which the present invention is applied is a so-called lithium ion battery, and as shown in FIG.
An electrode assembly including a positive electrode 2, a negative electrode 3, and a separator 4 is housed in a battery can 5. Further, a liquid non-aqueous electrolyte solution is injected as a non-aqueous electrolyte into the battery can 5.

The above electrode body contains a strip-shaped positive electrode 2 in which a positive electrode mixture layer 7 containing a positive electrode active material is formed on a positive electrode current collector 6, and a negative electrode active material on a negative electrode current collector 8. The strip-shaped negative electrode 3 on which the negative electrode mixture layer 9 is formed is the separator 4
And then wound in the longitudinal direction.

In the non-aqueous electrolyte battery 1 to which the present invention is applied, a polymer obtained by polymerizing a monomer molecule having at least one of the unit structures shown in Chemical formulas 6 and 7 below. (Hereinafter, simply referred to as “monomer”) is the positive electrode mixture layer 7
And / or added to the negative electrode mixture layer 9 as a binder.

[0018]

[Chemical 6]

[0019]

[Chemical 7]

The above polymer is a material that does not participate in the charge / discharge reaction of the non-aqueous electrolyte battery 1, and since the polymer itself does not expand or contract as the charge / discharge reaction proceeds, the positive electrode 2 to which this polymer is added And / or the negative electrode 3 is suppressed in expansion and contraction accompanying the charge / discharge reaction, as compared with the positive electrode and / or the negative electrode to which the polymer is not added. Further, since this polymer has high chemical resistance and has a property that it is difficult to swell with a non-aqueous electrolyte solution, a non-aqueous solvent or the like even at a relatively high temperature, the positive electrode 2 and / or the negative electrode 3 is Even when it expands and contracts due to the charge / discharge reaction, the decrease in the binding strength between the positive electrode current collector 6 and the positive electrode mixture layer 7 and the decrease in the binding strength between the negative electrode current collector 8 and the negative electrode mixture layer 9 are small.

Therefore, the non-aqueous electrolyte battery 1 has chemical formulas 6 and 7:
Since a polymer obtained by polymerizing a monomer molecule having at least one of the unit structures shown in is added to the positive electrode mixture layer 7 and / or the negative electrode mixture layer 9 as a binder. The cycle characteristics are improved as compared with the conventional non-aqueous electrolyte battery. In addition, the non-aqueous electrolyte battery 1 has excellent cycle characteristics, especially at high temperatures.

At least one of the unit structures shown in Chemical formulas 6 and 7 is contained in the monomer molecule constituting the polymer.
As long as the seed is contained, other unit structure may be contained, and it is more appropriate that the unit structure represented by the following chemical formula 8 is contained.

[0023]

[Chemical 8]

As the polymer, the unit structure shown in Chemical formula 6 is A, the unit structure shown in Chemical formula 7 is B, and the unit structure shown in Chemical formula 8 is C.
In this case, for example, as shown in Chemical formula 9, polymers (1) to (5) formed by polymerizing monomer molecules can be used. In addition,
In the polymers (a) to (e) shown in Chemical formula 9, n is 1
It is an integer above the above.

[0025]

[Chemical 9]

The polymer may contain a unit structure other than the unit structure shown in Chemical formula 8, for example, the unit structure shown in Chemical formulas 10 to 16 below in the monomer molecule.

[0027]

[Chemical 10]

[0028]

[Chemical 11]

[0029]

[Chemical 12]

[0030]

[Chemical 13]

[0031]

[Chemical 14]

[0032]

[Chemical 15]

[0033]

[Chemical 16]

Here, when the unit structure shown in Chemical formulas 10 to 16 is X, as the polymer, for example, polymers (6) to (13) shown in Chemical formula 17 can be used. In the polymers (6) to (13) shown in Chemical formula 17, m and n are 1
It is an integer above the above.

[0035]

[Chemical 17]

As the polymer, in particular, polyether sulfolane (PES) represented by the following chemical formula 18, polythioether sulfolane (PTES) represented by the chemical formula 19 below, and polyphenylene sulfide (PPS) represented by the chemical formula 20 below.
Is suitable to be added to the positive electrode 2 and / or the negative electrode 3. In the polymers shown in Chemical formula 18, Chemical formula 19, and Chemical formula 20, n is an integer of 1 or more.

[0037]

[Chemical 18]

[0038]

[Chemical 19]

[0039]

[Chemical 20]

Among the polymers (1) to (13) shown in Chemical formulas 9 and 17, one kind alone is used as the positive electrode 2 and /
Alternatively, it may be added to the negative electrode 3, or two or more kinds may be mixed and added to the positive electrode 2 and / or the negative electrode 3.

The degree of polymerization and the molecular weight of the polymer are appropriately selected and are not particularly limited. Particularly suitable polymers have a molecular weight of 3,000 or more, and more suitable polymers have a molecular weight of 30,000 or more.

When the polymer is in the form of powder particles, the particle size of the polymer is appropriately selected, but it is suitable that it is 0.1 μm or more and 40 μm or less. This is because if the particle size of the polymer is less than 0.1 μm, the particles may be too fine, which may make it difficult to form the positive electrode mixture layer 7 or the negative electrode mixture by coating. If the diameter is larger than 40 μm, it becomes larger than the particle diameters of other particles in the positive electrode mixture layer 7 or the negative electrode mixture, which makes handling difficult and may cause a minute short circuit inside the battery. is there.

The amount of the polymer added is appropriately selected, but is 0.1% by weight or more with respect to the positive electrode mixture layer 7, and 1
It is suitable to be added in the range of 5% by weight or less. This is because the amount of the polymer added to the positive electrode mixture layer 7 is 1
This is because if the amount exceeds 5% by weight, the proportion of the positive electrode active material in the positive electrode mixture layer 7 decreases, and the battery capacity required for practical use may not be achieved. This is because if the amount is less than 0.1% by weight, the desired effect may not be obtained.

The amount of these polymers added is appropriately selected, but is 1% by weight with respect to the negative electrode mixture layer 9.
As described above, it is appropriate that the content is added in the range of 40% by weight or less. This is because when the amount of the polymer added to the negative electrode mixture layer 9 exceeds 40% by weight, the proportion of the negative electrode active material in the negative electrode mixture layer 9 decreases, so that the battery capacity required for practical use may not be achieved. This is because if the amount of the polymer added to the negative electrode mixture layer 9 is less than 1% by weight, the desired effect may not be obtained.

In the positive electrode 2, a positive electrode mixture layer 7 containing a positive electrode active material is formed on a positive electrode current collector 6. Positive electrode current collector 6
For example, a metal foil such as an aluminum foil is used.

As the positive electrode active material, a metal oxide, a metal sulfide, a specific polymer or the like can be used depending on the type of the intended battery.

For example, when a lithium primary battery is constructed,
As the positive electrode active material, TiS ₂ , MnO ₂ , graphite, FeS
₂ etc. can be used.

When a lithium secondary battery is constructed,
As the positive electrode active material, a metal sulfide or oxide containing no lithium such as TiS ₂ , MoS ₂ , NbSe ₂ and V ₂ O ₅ , for example, a general formula Li _x MO ₂ (wherein M represents one or more transition metals). In the formula, x varies depending on the charge / discharge state of the battery, and is usually 0.05 ≦ x ≦ 1.10.), Such as a lithium composite oxide, can be used. The transition metal M constituting this lithium composite oxide includes Co, Ni, and M.
n or the like is used. Specifically, as the lithium composite oxide, LiCoO ₂ , LiNiO ₂ , and LiNi _y Co are used.
_{1-y O 2} (wherein, is 0 <y <1.), LiMn 2
O ₄ or the like can be used. These lithium composite oxides can generate a high voltage and become a positive electrode active material excellent in energy density. For the positive electrode 2, a plurality of these positive electrode active materials may be mixed and used.

When forming the positive electrode material mixture layer 7, a conventionally known conductive agent, binder or the like may be added.

In the negative electrode 3, a negative electrode active material layer containing a negative electrode active material is formed on the negative electrode current collector 8. Negative electrode current collector 8
For example, a metal foil such as a copper foil is used.

The negative electrode active material is appropriately selected according to the type of the intended battery. For example, in the case of a lithium primary battery or a lithium secondary battery, the negative electrode active material may be lithium, a lithium alloy, or lithium. A material or the like capable of occluding and releasing is used.

Materials capable of inserting and extracting lithium include
Carbon materials such as non-graphitizable carbon materials and graphite materials can be used. More specifically, pyrolytic carbons, cokes (pitch cokes, neat cokes, petroleum cokes, etc.), graphites, glassy carbons, organic polymer compound fired bodies (phenolic resins, furan resins, etc.) are suitable. Carbon materials such as carbonized by firing at temperature), carbon fibers, activated carbon, etc. can be used. As other materials capable of inserting and extracting lithium, polymers such as polyacetylene and polypyrrole, and oxides such as SnO ₂ can also be used.

When forming the negative electrode mixture layer 9, a conventionally known binder or the like can be added.

The non-aqueous electrolytic solution is prepared by dissolving an electrolyte salt in a non-aqueous solvent. As the non-aqueous solvent, any conventionally known non-aqueous solvent in this type of non-aqueous electrolyte battery can be used,
For example, cyclic carbonic acid esters such as propylene carbonate and ethylene carbonate, chain carbonic acid esters such as diethyl carbonate and dimethyl carbonate, carboxylic acid esters such as methyl propionate and methyl butyrate, γ-butyrolactone, sulfolane, 2
Ethers such as -methyltetrahydrofuran and dimethoxyethane can be used. These non-aqueous solvents may be used alone or in combination of two or more. Particularly, from the viewpoint of oxidation stability, it is preferable to use a carbonic acid ester together.

As the electrolyte salt, any of the conventionally known electrolyte salts in this type of non-aqueous electrolyte battery can be used. For example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCl
O ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ ,
_{LiC (SO 2 CF 3) 3} , LiAlCl 4, LiSi
Lithium salts such as F ₆ can be used. Among these electrolyte salts, LiBF ₄ or LiP is particularly preferable from the viewpoint of oxidation stability.
It is expedient to use F ₆ . It is preferable that the electrolyte salt is dissolved in a non-aqueous solvent to have a concentration of 0.1 to 3 mol / l, particularly 0.5 to 2.0 mol / l.

The shape of the non-aqueous electrolyte battery to which the present invention is applied is not limited to the cylindrical type described above, and may be any of a square type, a coin type, a button type, etc. It may be good.

Further, although the non-aqueous electrolyte battery using the liquid electrolyte, that is, the non-aqueous electrolyte has been described above, the present invention is not limited to this, and the non-aqueous electrolyte including the gel electrolyte or the solid electrolyte is also described. It can also be applied to batteries.

The gel electrolyte comprises a plasticizer containing a lithium salt and 10% to 50% by weight of a matrix polymer. The plasticizer contains esters, ethers, carbonic acid esters and the like. To form the gel electrolyte, the positive electrode mixture layer or the negative electrode mixture layer is impregnated with a solution containing a polymer compound, a plasticizer, and a solvent, and the solvent is removed to gel. A part of the gel electrolyte is impregnated in the positive electrode mixture layer or the negative electrode mixture layer to be gelled.

In the gel electrolyte, the proportion of the plasticizer is suitably 10% by weight or more and 80% by weight or less. This is because if the proportion of the plasticizer in the gel electrolyte exceeds 80% by weight, the ionic conductivity increases, but the mechanical strength may be too low. If less than 10% by weight, the mechanical strength will increase, but the ionic conductivity may decrease. The concentration of the electrolyte salt in the plasticizer is preferably 0.5 mol / l or more and 2.0 mol / l or less.

Examples of the matrix polymer include fluorine-based polymers such as poly (vinylidene fluorolide) and poly (vinylidene fluorolide-co-hexafluoropropylene), and ether-based polymers such as poly (ethylene oxide) and its crosslinked product. , Poly (acrylonitrile) and the like can be used. In particular, it is appropriate to use a fluoropolymer for the purpose of ensuring redox stability.

The solid electrolyte is composed of a lithium salt and a polymer compound. In order to form a solid electrolyte, the positive electrode mixture layer or the negative electrode mixture layer is impregnated with a solution containing a polymer compound, an electrolyte salt and a solvent, and the solvent is removed to solidify. A part of this solid electrolyte is impregnated into the positive electrode mixture layer or the negative electrode mixture layer to be solidified.

As the polymer compound, an ether polymer such as poly (ethylene oxide) or the same cross-linked polymer, a poly (methacrylate) ester polymer, an acrylate polymer or the like can be used. In addition, you may use these high molecular compounds individually or in mixture.

As the lithium salt, any conventionally known lithium-containing electrolyte salt in this type of non-aqueous electrolyte battery can be used.

[0064]

EXAMPLES A non-aqueous electrolyte secondary battery to which the present invention is applied will be described in detail below based on specific experimental results.

Sample 1 [Method for producing negative electrode] First, 90 parts by weight of a negative electrode active material,
Polyvinylidene fluoride (PVDF) 10 as a binder
After mixing with 1 part by weight, this mixture is mixed with N-methyl-2-
It was dispersed in pyrrolidone to obtain a negative electrode mixture slurry. Here, graphite (KS-75 manufactured by Lonza Co., Ltd.) was used as the negative electrode active material. The graphite used had a (002) plane spacing of 0.3358 nm.

Next, the negative electrode mixture slurry was uniformly applied to both surfaces of a strip-shaped copper foil having a thickness of 10 μm to be the negative electrode current collector, dried, and compression-molded using a roll press machine, followed by slitting. By doing so, a strip-shaped negative electrode was produced.

[Manufacturing Method of Positive Electrode] First, lithium carbonate and 1 mol of cobalt carbonate were mixed in a ratio of 0.5 mol: 1 mol, and the mixture was baked in air at 900 ° C. for 5 hours to obtain a positive electrode active material. Was synthesized as LiCoO ₂ .

Next, 91 parts by weight of LiCoO ₂ powder was added,
After mixing 6 parts by weight of graphite as a conductive agent and 3 parts by weight of polyvinylidene fluoride (PVDF) as a binder, the mixture was dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. did.

Next, this positive electrode material mixture slurry was uniformly applied to both surfaces of a strip-shaped aluminum foil having a thickness of 20 μm to be a positive electrode current collector, dried, and compression molded using a roll press machine. A slit-shaped positive electrode was produced by slitting.

[Preparation Method of Non-Aqueous Electrolyte] LiPF ₆ as an electrolyte salt was dissolved in a mixed solvent of equal volume of ethylene carbonate (EC) and diethyl carbonate at a ratio of 1.0 mol / l to prepare a non-aqueous electrolyte solution. An electrolytic solution was prepared.

[Cell Assembly Method] The strip-shaped negative electrode produced as described above, the strip-shaped positive electrode, and the separator having a thickness of 25 μm and made of a microporous polypropylene film were used as a separator, a negative electrode, a separator, and a positive electrode. Then, the spirally-wound electrode body was manufactured by laminating the separators in this order and winding the separators in the longitudinal direction a number of times.

Next, an insulating plate was inserted into the bottom of the nickel-plated iron battery can, and the electrode body was housed in this battery can. Next, in order to collect current from the negative electrode, one end of a nickel negative electrode lead was pressure-bonded to the negative electrode, and the other end was welded to a battery can. Next, in order to collect current from the positive electrode, one end of a positive electrode lead made of aluminum is attached to the positive electrode, and the other end is connected to the battery lid through a thin plate for current cutoff having a function of cutting off current in response to the internal pressure of the battery. Electrically connected.

Next, the non-aqueous electrolytic solution prepared as described above was poured into the battery can containing the electrode assembly, and the battery can was caulked through the asphalt-coated sealing gasket to form the battery lid. . As described above, the diameter is 18
A cylindrical non-aqueous electrolyte secondary battery having a size of mm and a height of 65 mm was produced.

Samples 2 to 9 When preparing negative electrodes, polyether sulfone (hereinafter referred to as PES) powder having an average particle size of 20 μm was added to the negative electrode mixture, and the amount of PES added to the negative electrode mixture was adjusted. A non-aqueous electrolyte secondary battery was produced in the same manner as in Sample 1 except that it was appropriately changed. The amount of PES added was as shown in Table 1 below.

Sample 10 A non-aqueous electrolyte secondary battery was prepared in the same manner as in Sample 1 except that hard carbon (hereinafter referred to as Hc) was used as the negative electrode active material. The hard carbon was prepared as follows. First, petroleum pitch was fired as a starting material in an inert gas stream at 1000 ° C. to obtain a non-graphitizable carbon material having properties close to glassy carbon, that is, hard carbon. When X-ray diffraction measurement was performed on this non-graphitizable carbon material, (00
2) Surface spacing is 3.76Å and true specific gravity is 1.58
It was g / cm ³ . Next, this non-graphitizable carbon material was crushed to obtain carbon powder having an average particle size of 10 μm, and this carbon powder was used as a negative electrode active material.

Sample 11 When producing a negative electrode, the average particle size was 20 with respect to the negative electrode mixture.
A non-aqueous electrolyte secondary battery was produced in the same manner as in Sample 10, except that 10% by weight of PES powder having a size of μm was added.

The samples 1 to 11 produced as described above were subjected to the charge / discharge test shown below to measure the initial discharge capacity, the battery capacity and the capacity retention rate, and the cycle characteristics under normal temperature environment and The cycle characteristics under high temperature environment were evaluated.

[Charge / Discharge Test] First, with respect to Samples 1 to 11, the charging current was set to 1 at 23 ° C.
The constant current and constant voltage charging as A was performed at an upper limit of 4.2 V for 3 hours. Next, constant current discharge with a discharge current of 700 mA was performed.
The final discharge voltage was measured up to a final voltage of 2.5V.

Next, with this charging / discharging cycle as one cycle, 500 cycles are performed in an environment of 23 ° C. for 50 cycles.
The discharge capacity at the 0th cycle was measured. Then, the ratio of the discharge capacity at the 500th cycle to the initial discharge capacity is obtained,
This was made into the capacity maintenance rate (unit:%) of the 500th cycle in 23 degreeC environment.

Next, a charge / discharge test was carried out for 500 cycles under a 60 ° C. environment, and the capacity retention ratio at the 500th cycle under a 60 ° C. environment was measured. Then, the ratio of the discharge capacity at the 500th cycle under the 60 ° C. environment to the initial discharge capacity under the 60 ° C. environment was calculated, and this was calculated as the capacity retention ratio at the 500th cycle under the 60 ° C. environment (unit:
%).

The above measurement results are shown in Table 1 together with the amount of PES added.

[0082]

[Table 1]

From Table 1, Samples 2 to 9 in which PES was added to the negative electrode mixture layer were compared with Sample 1 in which PES was not added to the negative electrode mixture layer, and the capacity at room temperature and 60 ° C. It can be seen that the maintenance rate is improved and the cycle characteristics are excellent under normal temperature and high temperature environments. Sample 11 in which PES is added to the negative electrode mixture layer
Is Sample 1 in which PES is not added to the negative electrode mixture layer
As compared with 0, the capacity retention ratio under normal temperature and high temperature environments is improved, and it can be seen that the cycle characteristics under normal temperature and high temperature environments are excellent.

Therefore, PES, that is, a polymer obtained by polymerizing a monomer molecule having at least one of the unit structures shown in Chemical formulas 6 and 7 is added to the negative electrode mixture layer as a binder. By doing so, it can be seen that a non-aqueous electrolyte secondary battery having excellent cycle characteristics under normal temperature and high temperature environments can be obtained.

Further, when comparing the sample 6 using graphite as the negative electrode active material and the sample 11 using non-graphitizable carbon (hard carbon), the sample 6 using graphite as the negative electrode active material is better. It can be seen that the improvement rate of the capacity retention rate is large and the improvement effect of the cycle characteristics is large. This is because graphite has a larger volume expansion / contraction ratio due to charge / discharge reaction than non-graphitizable carbon.

Further, comparing Samples 2 to 9, it can be seen that the capacity retention rate improves as the amount of PES added increases. However, since PES is a material that does not participate in the charge / discharge reaction, the larger the amount of PES added, the lower the initial capacity and the battery capacity after 500 cycles. On the other hand, the smaller the amount of PES added, the less the initial capacity decreases, but the improvement in capacity retention rate is also small.
It can be seen that the effect of improving the cycle characteristics is also small.

Therefore, PES in the negative electrode mixture layer,
That is, the amount of the polymer added is 1% by weight or more and 40% by weight.
By the following, it can be seen that a non-aqueous electrolyte secondary battery having a practical battery capacity and having very excellent cycle characteristics at room temperature and high temperature can be obtained.

When producing Samples 12 to 18 positive electrodes, polyethersulfone (PES) powder having an average particle size of 20 μm was added to the positive electrode mixture, and P
A non-aqueous electrolyte secondary battery was produced in the same manner as in Sample 1 except that the amount of ES added was changed appropriately. PE
The amount of S added was as shown in Table 2 below.

Sample 12 produced as described above
18, the charge and discharge test described above is performed in the same manner,
The initial discharge capacity, the battery capacity and the capacity retention rate were measured, and the cycle characteristics under the normal temperature environment and the high temperature environment were evaluated. The above measurement results are shown in Table 2 together with the amount of PES added.

[0090]

[Table 2]

From Table 2, LiCoO ₂ was used as the positive electrode active material.
Samples 12 to 18, in which PES is added to the positive electrode mixture layer, have higher capacity retention ratios at room temperature and 60 ° C. environment than Sample 1 in which PES is not added to the positive electrode mixture layer. It is understood that the cycle characteristics are excellent under normal temperature and high temperature environments.

In addition, comparing Samples 12 to 18, it can be seen that the capacity retention rate improves as the amount of PES added increases. However, since PES is a material that does not participate in the charge / discharge reaction, the larger the amount of PES added, the lower the initial capacity and the battery capacity after 500 cycles. On the other hand, the smaller the amount of PES added,
It can be seen that the decrease in initial capacity is small, but the improvement rate of capacity retention rate is small and the effect of improving cycle characteristics is small.

Therefore, PES for the positive electrode mixture layer,
That is, by adding the polymer in an amount of 0.1% by weight or more and 15% by weight or less, it is possible to obtain a non-aqueous electrolyte battery having a practical battery capacity and very excellent cycle characteristics at room temperature and high temperature. I understand.

Samples 19 to 25 Nonaqueous electrolyte secondary batteries were prepared in the same manner as in Sample 1 except that 10% by weight of the additives shown in Table 3 were added to the negative electrode mixture layer when the negative electrodes were prepared. did. In Table 3, polyether sulfone is referred to as PES, polythioether sulfone is referred to as PTES, polyphenylene sulfide is referred to as PPS, and polysulfone is referred to as PSU. The average particle size of these additives is approximately 20 μm.

Sample 26 Except that 10% by weight of PES was added to the negative electrode mixture layer when producing the negative electrode, and 3% by weight of PES was added to the positive electrode mixture layer when producing the positive electrode. A non-aqueous electrolyte battery was prepared in the same manner as in Sample 1.

Samples 19 to 19 produced as described above
For 26, the charge and discharge test described above is performed in the same manner,
The initial discharge capacity, the battery capacity and the capacity retention rate were measured, and the cycle characteristics under the normal temperature environment and the high temperature environment were evaluated. The above measurement results are shown in Table 3 together with the names and amounts of additives used.

[0097]

[Table 3]

From Table 3, PT was obtained as a polymer other than PES.
Even if ES, PPS or PSU is added to the negative electrode mixture layer, P
Like Samples 2 to 9 in which ES was added to the negative electrode mixture layer,
It can be seen that the effect of improving cycle characteristics can be obtained under normal temperature and high temperature environments. In addition, PES, PTES, PP
Even if S and PSU are used alone or in combination of two or more,
It can be seen that similar to Samples 2 to 9, it is possible to obtain the effect of improving cycle characteristics under normal temperature and high temperature environments.

Therefore, if it is a polymer obtained by polymerizing a monomer molecule having at least one of the unit structures shown in Chemical formulas 6 and 7, the positive electrode mixture layer and / or the negative electrode mixture described above is used. It can be seen that the effect of improving cycle characteristics can be achieved by being contained in the layer.

Further, from sample 26, the addition of PES to not only one of the positive electrode and the negative electrode but also the positive electrode and the negative electrode can obtain the effect of improving the cycle characteristics under normal temperature and high temperature environments. Recognize.

Sample 27 First, a positive electrode and a negative electrode were produced in the same manner as in Sample 1, except that the mixture layer was formed on one surface of the current collector.

Next, as a non-aqueous solvent, ethylene carbonate (E
C) 42.5 parts by weight and propylene carbonate (PC) 4
2.5 parts by weight and 15 parts by weight of LiPF ₆ as an electrolyte salt were mixed to prepare a plasticizer. Next, 30 parts by weight of the above plasticizer and poly (vinylidene fluoride-co-
10 parts by weight of hexafluoropropylene) and 60 parts by weight of diethyl carbonate were mixed and dissolved to prepare a gel electrolyte solution.

Next, a gel electrolyte solution was uniformly applied and impregnated on the main surfaces of the positive electrode active material and the negative electrode active material, and allowed to stand at room temperature for 8 hours to vaporize dimethyl carbonate.
A gel electrolyte was formed on the positive electrode active material and the negative electrode active material.

Next, the positive electrode and the negative electrode were laminated via a gel electrolyte and pressure-bonded to form an electrode body. Next, by accommodating the electrode body including the gel electrolyte in the exterior material, the vertical width is 2.5 cm, the horizontal width is 4.0 cm, and the thickness is 0.3 mm.
A flat plate type gel electrolyte battery was manufactured.

Sample 28 When the negative electrode was prepared, the average particle size was 20 μm with respect to the negative electrode mixture.
A gel electrolyte battery was produced in the same manner as in Sample 27 except that 10% by weight of PES powder of m was added.

The sample 27 produced as described above,
The following charge / discharge test was performed on No. 28, the initial discharge capacity, the battery capacity and the capacity retention rate were measured, and the cycle characteristics under the normal temperature environment and the cycle characteristics under the high temperature environment were evaluated.

[Charge / Discharge Test] First, in a 23 ° C. environment, constant-current constant-voltage charging at a charging current of 10 mA was performed at an upper limit of 4.2 V for 3 hours. Next, constant current discharge with a discharge current of 6 mA was performed up to a final voltage of 2.5 V, and the initial discharge capacity was measured.

Next, when this charging / discharging cycle is defined as 1 cycle, 500 cycles are performed in an environment of 23 ° C.
The discharge capacity at the 500th cycle was measured. And 50
The ratio of the discharge capacity at the 0th cycle to the initial discharge capacity was obtained, and this was taken as the capacity retention rate (unit:%) at the 500th cycle under a 23 ° C. environment.

Next, a charge / discharge test was carried out for 500 cycles in an environment of 60 ° C., and the capacity retention ratio at the 500th cycle was measured. Then, the ratio of the discharge capacity at the 500th cycle under the 60 ° C environment to the initial discharge capacity under the 60 ° C environment was obtained, and this was taken as the capacity retention rate (unit:%) at the 500th cycle under the 60 ° C environment.

The above measurement results are shown in Table 4 together with the amount of PES added.

[0111]

[Table 4]

From Table 4, the sample 28 in which PES was added to the negative electrode mixture layer was compared with the sample 27 in which PES was not added to the negative electrode mixture layer, and the capacity retention ratio at room temperature and 60 ° C. It can be seen that the cycle characteristics at room temperature and high temperature are excellent. Therefore, it is understood that the present invention can be applied to a battery including a gel electrolyte regardless of the type of electrolyte.

[0113]

As is apparent from the above description, in the non-aqueous electrolyte battery according to the present invention, monomer molecules having at least one of the unit structures shown in Chemical formulas 6 and 7 are polymerized. Since the polymer thus obtained is added to the positive electrode mixture layer and / or the negative electrode mixture layer, expansion and contraction of the positive electrode and the negative electrode due to the charge / discharge reaction are suppressed. Therefore, the non-aqueous electrolyte battery according to the present invention is excellent not only in room temperature but also in cycle characteristics at high temperature.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a non-aqueous electrolyte battery.

[Explanation of symbols]

1 Non-Aqueous Electrolyte Battery, 2 Positive Electrode, 3 Negative Electrode, 4 Separator, 5 Battery Can, 6 Positive Electrode Current Collector, 7 Positive Electrode Mixture Layer, 8
Negative electrode current collector, 9 Negative electrode mixture layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Tomita             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Ken Segawa             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Sam Hui             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 5H029 AJ05 AK02 AK03 AK05 AL06                       AL07 AL08 AL12 AM02 AM03                       AM04 AM05 AM07 AM16 BJ02                       BJ03 BJ04 BJ14 DJ08 EJ12                       HJ01                 5H050 AA05 AA07 BA16 BA17 BA18                       CA02 CA08 CA11 CB07 CB08                       CB12 DA11 EA23 FA05 HA01

Claims (6)

[Claims] 1. A non-aqueous electrolyte battery comprising a positive electrode having a positive electrode mixture layer containing a positive electrode active material, a negative electrode having a negative electrode mixture layer containing a negative electrode active material, and a non-aqueous electrolyte. A polymer obtained by polymerizing a monomer molecule having at least one of the unit structures shown in Chemical formula 2,
A non-aqueous electrolyte battery, which is added to the positive electrode mixture layer and / or the negative electrode mixture layer. [Chemical 1] [Chemical 2] 2. The non-aqueous electrolyte battery according to claim 1, wherein the monomer molecule has a unit structure shown in Chemical formula 3 below. [Chemical 3] 3. The non-aqueous electrolyte according to claim 1, wherein the polymer is added in the range of 0.1% by weight or more and 15% by weight or less with respect to the positive electrode mixture layer. battery. 4. The non-aqueous electrolyte battery according to claim 1, wherein the polymer is added in an amount of 1% by weight or more and 40% by weight or less with respect to the negative electrode mixture layer. 5. The non-aqueous electrolyte battery according to claim 1, wherein the positive electrode active material contains a metal oxide or a metal sulfide. 6. The non-aqueous electrolyte battery according to claim 1, wherein the negative electrode active material contains lithium, a lithium alloy, or a material capable of inserting and extracting lithium.