CN1795578A - Lithium ion secondary battery - Google Patents

Abstract

A lithium ion secondary battery includes a positive electrode capable of absorbing and desorbing lithium ion, a negative electrode capable of absorbing and desorbing lithium ion, a porous film interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte: the porous film being adhered to a surface of at least one of the positive electrode and the negative electrode; the porous film including a filler and a resin binder; the resin binder content in the porous film being 1.5 to 8 parts by weight per 100 parts by weight of the filler; and the resin binder including an acrylonitrile unit, an acrylate unit, or a methacrylate unit.

Description

Lithium rechargeable battery

Technical field

The present invention relates to a kind of lithium rechargeable battery with following perforated membrane, wherein said perforated membrane is made of filler and resin binder, and surperficial bonding with at least one side of anodal and negative pole.The present invention relates to a kind of lithium rechargeable battery,, and have excellent safety even its short circuit can not produce thermal runaway yet.

Background technology

Along with electronic equipment to development removable, wireless aspect, as its driving power, noticeable is small-sized, light weight and the lithium rechargeable battery with high-energy-density.Lithium rechargeable battery has: the positive pole that is made of transition metal oxide that contains lithium etc., the negative pole and the nonaqueous electrolytic solution that are made of material with carbon element etc.

In lithium rechargeable battery, barrier film is between positive pole and negative pole, and wherein said barrier film has the effect that produces electric insulation between two electrodes and keep electrolyte that makes.This barrier film mainly uses the microporous barrier that is made of polyolefin such as polyethylene, polypropylene.Microporous barrier is generally processed by resin stretched.

But such barrier film probably just produces thermal contraction under the lower temperature about 100 ℃.Therefore, might cause thermal runaway because of the rapid expansion of minute short circuit portion.That is to say, if having impurity sneak into or because of nail thorn test produces short circuit, then under the effect of the heat of moment generation, just barrier film produces thermal contraction.Thus, the defective part of barrier film increases, and short circuit enlarges, so that causes thermal runaway.Particularly surpassing under 150 ℃ the environment, because the contraction of microporous barrier, the possibility that battery security is destroyed is bigger.

So, as Fig. 4 schematically illustrate, study as the project that barrier film plays a role with regard to paste electrolyte 40.Paste electrolyte 40 is comprising the filler grain 42 of a large amount of electrolyte 41 of containing tackifier and electrical insulating property, filler grain 42 as anodal 43 and negative pole 44 between dividing plate (spacer) play a role (opening flat 10-55718 communique) with reference to the spy.

Because paste electrolyte is to adopt tackifier to improve the composite material of the filler of the electrolyte of viscosity and electrical insulating property,, can guarantee the lithium-ion-conducting of certain level so its advantage is fully to contain electrolyte.But its shortcoming is that the intensity as barrier film is inadequate, thereby lacks practicality.

In addition, the someone has proposed following perforated membrane as the scheme of barrier film, and wherein said perforated membrane is made of filler and resin binder, and with at least one side's of positive pole and negative pole surperficial bonding (opening flat 10-106530 communique) with reference to the spy.

Perforated membrane adopts following method to form: be about to by filler and be dissolved in raw material paste coating that the resin binder in the solvent constitutes at polar board surface, carry out drying then.In such paste,, contain fluororesin, vistanex etc. as resin binder.

Moreover, for prevent in the manufacturing process of battery, electrode composition partly comes off and brings out the internal short-circuit of battery from pole plate, also proposed and with the scheme (spy opens flat 7-220759 communique) of above-mentioned perforated membrane and barrier film.

Te Kaiping 10-106530 communique is to guarantee the intensity and the fail safe of certain level with the special advantage of driving the described perforated membrane of flat 7-220759 communique.

But, after making resin binder be dissolved among the solvent, when resin binder is separated out on the filler grain surface, as Fig. 5 schematically illustrate, because the area of the filler grain 52 that covers with resin binder 51 increases, so must use a large amount of resin binders.Its result, opposite with intensity, reduce in space between filler grain, thereby tend to make anodal 53 and negative pole 54 between electrolyte or the mobile path of lithium ion become insufficient.That is to say, be difficult to when keeping certain intensity, guarantee the conductibility of sufficient lithium ion.

In addition, as the resin binder of perforated membrane, because the resin that does not have discovery to have suitable rerum natura, so when keeping lithium-ion-conducting, seeking further to improve perforated membrane intensity also is the comparison difficulty.

Summary of the invention

The present invention relates to a kind of lithium rechargeable battery with following perforated membrane, wherein said perforated membrane is made of filler and resin binder, and surperficial bonding with at least one side of anodal and negative pole.

One of purpose of the present invention provides a kind of lithium rechargeable battery, it is by using following perforated membrane, fail safe and high-rate characteristics are had both, wherein said perforated membrane is defined as the content of the resin binder in the perforated membrane on a small quantity, select the formation monomer of resin binder simultaneously, can guarantee the conductibility of thermal endurance, necessary strength and lithium ion by this.

For improving the lithium-ion-conducting of perforated membrane, must in perforated membrane, form space as much as possible.In addition, in order in perforated membrane, to form a large amount of spaces, must reduce the consumption of resin binder with respect to filler as far as possible.But,,, just can not improve lithium-ion-conducting to greatest extent if the size in space is unwell to moving of lithium ion even in perforated membrane, form a large amount of spaces.In view of this, one of purpose of the present invention is by the average pore size of micropore in the control perforated membrane, and the lithium-ion-conducting of perforated membrane is improved to greatest extent.

Be formed with on the pole plate of perforated membrane,,, thereby causing poor short circuit so perforated membrane might produce be full of cracks because when constituting the pole plate group, apply tensile stress.The tolerance of perforated membrane counter stress though also be subjected to the coating condition of the raw material paste that is made of filler and resin binder and the influence of drying condition, finally exists with ... the percentage elongation of perforated membrane strongly.Yet, in order to ensure the lithium-ion-conducting of perforated membrane, the content of resin binder must be defined as on a small quantity, even the control of percentage elongation is all had no time, and it turns round and look at.In view of this, one of purpose of the present invention is by the percentage elongation of control perforated membrane, and the reliability of battery is improved.

When resin binder being defined as when a small amount of, though favourable to the flash-over characteristic of battery, the porous film strength reduces, and is easy to generate crackle.In case perforated membrane comes off from pole plate, will bring out internal short-circuit, cause the reduction of battery product qualification rate.Particularly under the situation of formation lithium rechargeable battery of reeling, positive pole and negative pole are wound into helical form by the separation of barrier film.In the part that begins to reel, because radius of curvature is less, thereby the bending stress increase, so that perforated membrane breaks easily.In view of this, one of purpose of the present invention is by the control distribution of resin binder on the perforated membrane thickness direction, when keeping the battery discharge characteristic, suppresses because of the mixture that produces in the manufacturing process caused internal short-circuit that comes off by means of perforated membrane.

The present invention relates to a kind of lithium rechargeable battery, it constitutes: can embed/positive pole of removal lithium embedded ion, can insert/take off the negative pole of inserting lithium ion, perforated membrane between described positive pole and negative pole and nonaqueous electrolytic solution; At least one side's of wherein said perforated membrane and described positive pole and negative pole is surperficial bonding; Described perforated membrane is made of filler and resin binder; The content of described resin binder in described perforated membrane is that the described filler with respect to per 100 weight portions is 1.5～8 weight portions; Described resin binder contains acrylonitrile unit, acrylic ester unit or methacrylate unit.

The invention still further relates to a kind of lithium rechargeable battery, wherein the average pore size of micropore is 0.02～0.09 μ m in the described perforated membrane of being tried to achieve by the bubble point method.

The present invention relates to a kind of lithium rechargeable battery again, the percentage elongation of wherein said perforated membrane be 15% or more than.

The present invention relates to a kind of lithium rechargeable battery again, and the amount of wherein said resin binder is less in the 1st face side that described perforated membrane and described electrode surface are bonding, and is more in the 2nd face side of the relative side on described the 1st surface.

Described filler preferably is made of the mixture of macroparticle group and small-particle group, and the average grain diameter B of the average grain diameter A of described macroparticle group and described small-particle group satisfies formula (1): 0.05≤B/A≤0.25.

Described resin binder is made of core-shell (core-shell) type rubber particles, and described rubber particles preferably has the adhesiveness skin section.

Described filler preferably contains Al at least ₂O ₃

Described resin binder preferably has 250 ℃ or above temperature of initial decomposition.

Described resin binder preferably has 250 ℃ or above crystalline melting point (crystallinemelting point).

The invention still further relates to a kind of lithium rechargeable battery, wherein said perforated membrane is made of 1 tunic, and the amount of described resin binder increases gradually from described the 2nd face side of described the 1st surface lateral.

The present invention relates to a kind of lithium rechargeable battery again, wherein said perforated membrane is made of multilayer film, and the described resin binder that is arranged in the film of described the 2nd face side is arranged in the described resin binder of film of described the 1st face side at the shared ratio height of the total amount of described filler and described resin binder at the shared ratio of the total amount of described filler and described resin binder.

In the skin section of described the 2nd face side of described perforated membrane, described filler shared ratio in the total amount of described filler and described resin binder is preferably 70～98 weight %, and the thickness of described skin section is preferably 20% of described perforated membrane thickness.

The present invention relates to a kind of lithium rechargeable battery, wherein said positive pole and described negative pole are wound into helical form in the mode across described perforated membrane only.

The invention still further relates to a kind of lithium rechargeable battery, wherein said positive pole and described negative pole are wound into helical form in the mode across described perforated membrane and barrier film.

The present invention relates to the manufacture method of described lithium rechargeable battery, it has following operation:

(a) the allotment paste makes it to contain: the filler of 100 weight portions, the resin binder that contains acrylonitrile unit, acrylic ester unit or methacrylate unit of 1.5～8 weight portions, and the decentralized medium of described filler; (b) with described paste coating at least one side's of anodal and negative pole surface; (c) under 100 ℃～180 ℃ temperature, the paste that is coated in described electrode surface is carried out drying.

According to the present invention, because the resin-bonding agent content in the perforated membrane is restricted on a small quantity, and resin binder contains acrylonitrile unit, acrylic ester unit or methacrylate unit, thereby can provide a kind of following lithium rechargeable battery, it can guarantee the balance between thermal endurance, necessary strength and the lithium-ion-conducting well, and takes into account fail safe and high-rate characteristics.

According to a scheme of the present invention, because the average pore size of micropore in the perforated membrane is controlled at 0.02～0.09 μ m, thereby can provide the good lithium rechargeable battery of flash-over characteristic such as high-rate characteristics.

According to a scheme of the present invention,, thereby can provide the lithium rechargeable battery of taking into account charge-discharge characteristic and reliability because what use is the perforated membrane that percentage elongation is controlled and the inner stress that produces of pole plate group is had abundant tolerance.

According to a scheme of the present invention, since use be resin binder amount less with bonding the 1st face side of electrode surface, at the more perforated membrane of the 2nd face side of its relative side, thereby when guaranteeing the flexibility of perforated membrane, can also fully guarantee the gap that lithium ion is moved in the electrode surface side.In addition, because perforated membrane has flexibility, thereby can suppress the coming off of perforated membrane in the manufacturing process, and can suppress internal short-circuit.Therefore, can provide lithium rechargeable battery high-quality, high security.

Description of drawings

Fig. 1 is a schematic diagram of representing the formation of perforated membrane of the present invention.

Fig. 2 is expression and the schematic diagram of an example of the configuration of the bonding electrode of perforated membrane of the present invention.

Fig. 3 is the longitudinal profile schematic diagram of an example of lithium rechargeable battery of the present invention.

Fig. 4 is a schematic diagram of representing the formation of barrier film in the past.

Fig. 5 represents the schematic diagram of the formation of other barrier film in the past.

Fig. 6 is the FT-IR absorption spectrum of an example of core-shell rubber particles.

Fig. 7 is the longitudinal profile schematic diagram of an example of lithium rechargeable battery of the present invention.

Embodiment

The present invention relates to a kind of lithium rechargeable battery, it constitutes: can embed/positive pole of removal lithium embedded ion, can insert/take off the negative pole of inserting lithium ion, perforated membrane between described positive pole and negative pole and nonaqueous electrolytic solution.

At least one side's of perforated membrane and anodal and negative pole is surperficial bonding, and perforated membrane is made of filler and resin binder.

The content of the resin binder in the perforated membrane is 1.5～8 weight portions with respect to the filler of per 100 weight portions.

When the resin-bonding agent content in the perforated membrane is lower than 1.5 weight portions with respect to per 100 weight portion fillers, the perforated membrane that just can not obtain having abundant intensity.In addition, can't obtain having the perforated membrane of suitable percentage elongation.

On the other hand, when the content of resin binder surpasses 8 weight portions with respect to per 100 weight portion fillers, just can not in perforated membrane, form sufficient space, thereby cause high-rate characteristics to descend.In addition, also being difficult to size with the space is controlled at and is suitable in the scope that lithium ion moves.

Resin binder contains acrylonitrile unit, acrylic ester unit or methacrylate unit.

Just in case under the situation that produces internal short-circuit, the heating temp of short circuit portion will reach about 100 ℃.Therefore, under the lower situation of the temperature of initial decomposition of resin binder and crystalline melting point, perforated membrane will deform, and probably cause the expansion of short position.From avoiding the angle of this unfavorable condition, resin binder preferably has 250 ℃ or above temperature of initial decomposition.In addition, have under the crystalline situation, preferably have 250 ℃ or above crystalline melting point at resin binder.In addition, so-called crystalline melting point means the temperature that crystalline polymer begins to soften.

Here, resin binder preferably comprises the core-shell rubber particles with adhesiveness skin section, even this rubber particles is a small amount of, also can give play to sufficient bonding effect.

Under the situation of using the core-shell rubber particles, the form with point is bonded together between the filler grain because can make, so, can guarantee more space in perforated membrane inside, can guarantee the mobile path of electrolyte or lithium ion fully.In addition, perforated membrane can be guaranteed the tolerance of counter stress fully.

Fig. 1 has schematically illustrated its form.Because be bonded together by the form of core-shell rubber particles 11 between the filler grain 12 with point, so, between positive pole 13 and negative pole 14, can guarantee to have a large amount of space 15.Therefore, because moving of electrolyte or lithium ion can not be subjected to big obstruction, thereby can fully guarantee the conductibility of lithium ion, can keep good speed characteristic.That is to say, make lithium ion move path guarantee become easy.In addition and since with the point form be bonded together, even thereby use a spot of rubber particles, also can guarantee the intensity and the percentage elongation of barrier film.

The average grain diameter of rubber particles is 0.05～0.3 μ m, and this is preferred obtaining to keep between intensity and the voidage aspect the perforated membrane of balance preferably.

The adhesiveness skin section of core-shell rubber particles preferably contains acrylic ester unit.As acrylic ester unit, 2-EHA is suitable.

All the time, the employed resin material of battery selected is index with the stability of the resin of deriving from molecular orbital method (HOMO/LUMO).According to such index, the resin or their combination (copolymer) of selected one pack system usually.Therefore, contain the resin binder of unsettled acrylonitrile unit under the negative pole current potential,, be difficult to select from viewpoint in the past.

When combination various kinds of resin adhesive was used for perforated membrane, core-shell rubber particles shared ratio in all resins adhesive was preferably 20～80 weight %.

When combination various kinds of resin adhesive is used for perforated membrane, resin binder as beyond the core-shell rubber particles can use Kynoar fluororesin such as (PVDF), carboxymethyl cellulose celluosic resins such as (CMC), polyvinylpyrrolidone (PVP) etc.In addition, consider with the angle of appropriate viscosity, preferably fluororesin (for example molecular weight is 100,000～1,000,000 PVDF) is waited and core-shell rubber particles and usefulness from the raw material paste of giving perforated membrane.

Consider from the angle of balance adhesiveness and caoutchouc elasticity, measuring by the FT-IR of core-shell rubber particles in the absorption spectrum that obtains, be preferably 3～50 times based on the absorption intensity of the C ≡ N stretching vibration of acrylonitrile unit based on the absorption intensity of C=O stretching vibration.When based on the absorption intensity deficiency of C=O stretching vibration during based on 3 times of the absorption intensity of C ≡ N stretching vibration, it is insufficient that the bonding effect of rubber particles just becomes, and when surpassing 50 times, it is insufficient that the caoutchouc elasticity of rubber particles just becomes, thereby the porous film strength is reduced.In addition, so-called absorption intensity is meant the height of the absworption peak of seeing from the baseline of spectrum.

In FT-IR measured, the absorption spectrum of core-shell rubber particles for example can use the sample that is coated with this rubber particles on the KBr plate to measure.In general, based on the absorption of C=O stretching vibration, can be at 1700～1760cm ^-1Near observe, based on the absorption of C ≡ N stretching vibration, can be at 2200～2280cm ^-1Near observe.

(with the volume is the median particle diameter D of benchmark to the average grain diameter of filler ₅₀) be preferably 0.2～2 μ m.When average grain diameter is excessive, then be difficult to form thin (for example thickness is about 20 μ m) and the perforated membrane of homogeneous, and when too small, then along with the long-pending increase of filling surface, the amount of necessary resin binder also increases, so that is difficult to form in perforated membrane sufficient space.

In addition, from the occupied state that makes filler near the angle of the most closely knit filling or the control of the average pore size in space is become be easy to angle and consider that filler preferably is made of the mixture of macroparticle group and small-particle group.When producing stress in the perforated membrane that is in the most closely knit occupied state, because of " slips " of filler grain relaxed stress, so even the increase percentage elongation also makes membrane structure keep easily.

(with the volume is the median particle diameter D of benchmark to the average grain diameter A of macroparticle group ₅₀) be preferably 0.2～2 μ m.In addition, (with the volume is the median particle diameter D of benchmark to the average grain diameter B of small-particle group ₅₀) be preferably 0.01～0.5 μ m.

The average grain diameter B of the average grain diameter A of macroparticle group and small-particle group preferably satisfies formula (1): 0.05≤B/A≤0.25.When the B/A value was lower than 0.05, the surface area of filler became excessive, was difficult to obtain the sufficient perforated membrane of intensity by the use of low amounts of resin adhesive.The amount of resin binder is increased, so that there is the tendency of minimizing in the space in the perforated membrane.On the other hand, when the B/A value surpassed 0.25, the space that forms between the filler then excessively increased, thereby the appearance of capillarity is suppressed, and causes the decline of high-rate characteristics on the contrary.In addition, because the space that forms increases between the filler, thereby the slip of filler is suppressed, so that the percentage elongation of perforated membrane is reduced.

All the ratio of the small-particle group that is contained in the filler is preferably 1～20 weight %, and surplus is the macroparticle group.When the ratio of small-particle group is very few, the closely knit filling of the filler difficulty that becomes, and the ratio of small-particle group is when too much, the surface area of filler excessively increases, and is difficult to obtain the sufficient perforated membrane of intensity by the use of low amounts of resin adhesive.

Filler is preferably by containing aluminium oxide (Al at least ₂O ₃) inorganic oxide constitute.In inorganic oxide, other can use titanium oxide (TiO ₂), silica (SiO ₂) etc.They can use separately, also can make up two or more uses.But, Al ₂O ₃In whole fillers shared ratio be preferably 50 weight % or more than.

Here, as using Al at least ₂O ₃Reason, can be listed below: (1) Al ₂O ₃Median particle diameter be suitable for forming the desired microcellular structure of perforated membrane (median particle diameter is 0.02～0.09 μ m); (2) (0～5V/vs.Li) all stablizes to oxidation and reduction potential; (3) concavo-convex less (surface area is less) of particle surface, thus use a spot of resin binder just to obtain high-intensity perforated membrane etc. easily.

Perforated membrane is coated with this raw material paste at least one side's of anodal and negative pole surface, if necessary, and just can be by drying to obtain with the bonding state in this surface.Drying was preferably carried out under 50～150 ℃ 1 minute～30 minutes.The desciccator diaphragm that forms at electrode surface also can make it to become perforated membrane by calendering after this as required.

The raw material paste of perforated membrane is allocated by filler and resin binder are dispersed.Liquid parts as this moment can make water, N-N-methyl-2-2-pyrrolidone N-(hereinafter referred to as NMP), acetone, lower alcohol etc., also can use nonaqueous electrolytic solution.

The content of the raw material in the raw material paste of perforated membrane (total amount of filler and resin binder) is preferably 25～70 weight %.When material content is very few, be difficult to form perforated membrane with desirable thickness and intensity, when material content was too much, paste viscosity increased and makes coating become difficult.

In the preferred scheme of the present invention, the average pore size in the space that the perforated membrane that is made of filler and resin binder is tried to achieve by the bubble point method is controlled as 0.02～0.09 μ m.

Even can guarantee to have a large amount of spaces in perforated membrane, the average pore size when the space is lower than 0.02 μ m, also because be added with the mobile obstruction that is subjected to filler grain and resin binder of the lithium ion of solvent, makes the conductibility of lithium ion become insufficient.On the other hand, when the average pore size in space surpasses 0.09 μ m, just can not effectively utilize the capillarity that promotes that lithium ion moves, so that lithium-ion-conducting is still insufficient.

Here, the average pore size in the space in the perforated membrane can be tried to achieve by bubble point method (ASTM F316-86, JIS K3832).Specifically, average pore size d can try to achieve as median particle diameter by the following method.

(1) at first, add air pressure, obtain the relation between air pressure P (Psi) and the air mass flow by perforated membrane (dry flow D, unit are rise/minute) from the single face of the perforated membrane that is in drying regime.

(2) secondly, make the interior space lyosoption (water, alcohol etc.) of perforated membrane afterwards, just the single face at perforated membrane forms the interface that contacts with solvent, add air pressure from its back side, obtain the relation between air pressure P (Psi) and the air mass flow by perforated membrane (moistening flow W, unit are rise/minute).At this moment, will can observe the minimum pressure (bubble point) that bubble produces at porous film surface and be set at P _oThe W value of this moment is 0, and when P reached certain value, the D value became consistent with the W value.The minimum pressure that the D value is consistent with the W value is set at P _s

(3) from P _oTo P _sPressure limit in, obtain the relation between P and the Δ (W/D), utilize the relation of d=0.451 γ/P (γ: the surface tension of water, unit are mN/m), it is converted into relation between d and the Δ (W/D).

(4) scaled value from obtaining is obtained the distribution of the flow percentage Q that is defined as Q=Δ (W/D) * 100, and the intermediate value of the d in this distribution is exactly d.Obtaining the not special restriction of interval width of the P value when distributing, for example is 150～250Psi.

When the average pore size in the space that obtains to be tried to achieve by the bubble point method was the perforated membrane of 0.02～0.09 μ m, resin binder also preferably comprised the core-shell rubber particles with adhesiveness skin section.

As not special qualification of method of the average pore size of control perforated membrane internal pore, the control of average grain diameter can wait by the viscosity of raw material paste, drying condition, rolling condition after the electrode surface coating to be carried out.

Because suitable condition is difference according to the difference of the kind of battery etc., cannot treat different things as the same, but, for example when for the time with the same battery of embodiment described later 1, then the viscosity of preferred feedstock paste is 1000～100000cP, baking temperature after the electrode surface coating is 45～200 ℃, and the line pressure of calendering is about 1～1000kgf/cm.

In the preferred scheme of the present invention, the percentage elongation of the perforated membrane that constitutes by filler and resin binder be controlled in 15% or more than.

Even in perforated membrane, can guarantee to have a large amount of spaces, but when the percentage elongation of perforated membrane is insufficient, can not tolerate the stress of pole plate group inside.Consider from the angle that suppresses short circuit and take place, obtain the high battery of reliability, the percentage elongation that requires perforated membrane be 15% or more than.

When percentage elongation was lower than 15%, for example under the situation of winding pole, the possibility that then produce be full of cracks on perforated membrane, is short-circuited increased.Be full of cracks takes place in the interior perimembranous of the radius of curvature minimum that is caused by coiling easily.The diameter R of the interior perimembranous of perforated membrane is just about 3mm.Here, percentage elongation can be measured according to the method for stipulating among the JIS C2318.

In the preferred scheme of the present invention, the content of the resin binder in the perforated membrane that constitutes by filler and resin binder, less in the 1st face side, more in the 2nd face side.Wherein, so-called the 1st surface is and the surface of the bonding side of the electrode surface of perforated membrane that so-called the 2nd surface is the surface of its relative side.

Perforated membrane can be made of 1 tunic, also can be to be made of multilayer film.

The perforated membrane that is made of 1 tunic can obtain by following method, and promptly the raw material paste that coating contains filler, resin binder and liquid parts on electrode carries out drying then.Adopt drying means to accelerate the evaporation rate of liquid parts, when making the liquid parts volatilization, resin binder is moved to the 2nd face side of perforated membrane by this.Its result, from 2nd face side of electrode surface to perforated membrane, the content of resin binder increases progressively gradually.That is to say,, formed the concentration gradient of resin binder at the thickness direction of perforated membrane.

The baking temperature of the raw material paste that applies on the electrode is preferably 100 ℃～180 ℃.When baking temperature is lower than 100 ℃, the speed of liquid parts volatilization is slowed down, at the thickness direction of perforated membrane, it is even that the CONCENTRATION DISTRIBUTION of resin binder becomes usually.On the other hand, when baking temperature was higher than 180 ℃, in perforated membrane the 2nd face side, resin binder was too much usually.Its result, the absorbency of perforated membrane and electrode pair electrolyte is hindered, thus the guiding discharge characteristic descends.

Secondly, can make by following method by the perforated membrane that multilayer film constitutes.At first, allocate the raw material paste of the different perforated membrane of various kinds of resin binder content.The initial raw material paste that the application of resin binder content is lower on electrode also carries out drying, thereby forms the 1st tunic.Then, the higher raw material paste of application of resin binder content and carry out drying on the 1st tunic, thus form the 2nd tunic.When perforated membrane is made of 3 layers or more multi-layered film, re-use the higher raw material paste of resin-bonding agent content, repeat same operation.That is to say, on electrode according to the resin-bonding agent content from low paramount order, the raw material paste that the application of resin binder content is different also carries out drying, thereby film is formed.

Formation is compared with the method that forms the perforated membrane that is made of 1 tunic by the method for the perforated membrane that multilayer film constitutes, and the advantage that has is the content that can at random change the resin binder in each tunic.In addition, also can stackedly contain the multilayer film of different fillers separately and form perforated membrane.

In the method that forms the perforated membrane that is made of 1 tunic, preferably resin binder is dissolved in the liquid parts.On the other hand, in the method that forms the perforated membrane constitute by multilayer film, even be not dissolved in the liquid parts, the resin binder that for example just is dispersed in the liquid parts also can suit to use.

In the skin section of the 2nd face side of perforated membrane, filler shared ratio in the total amount of filler and resin binder is preferably 70 weight %～98 weight %, more preferably 90～98 weight %.Wherein, the thickness of " skin section " is defined as 20% of perforated membrane thickness here.

In the skin section of the 2nd face side of perforated membrane, the content that surpasses 98 weight %, resin binder in filler shared ratio in the total amount of filler and resin binder is lower than under the situation of 2 weight %, when operation such as pole plate being reeled, often can not suppress the cracking of perforated membrane.

In addition, in the skin section of the 2nd face side of perforated membrane, when the content that filler shared ratio in the total amount of filler and resin binder is lower than 70 weight %, resin binder surpassed 30 weight %, the absorbency of perforated membrane and electrode pair electrolyte was hindered.

Positive pole and negative pole that the present invention for example goes for only separating by barrier film are wound as spiral helicine lithium rechargeable battery.At this moment, consider that from giving full play to the angle of keeping the design capacity of battery by the function of electric insulation functions between the pole plate of perforated membrane generation and fail safe raising, simultaneously the thickness of perforated membrane is preferably 10～50 μ m, more preferably 10～30 μ m.Under the situation that forms the perforated membrane that is made of multilayer film, the gross thickness of perforated membrane also is preferably set to 10～50 μ m, further is preferably set to 10～30 μ m.

In addition, the present invention also goes for and will be wound as spiral helicine lithium rechargeable battery by the positive pole and the negative pole of perforated membrane and barrier film separation.At this moment, the thickness of perforated membrane does not have special restriction, and from giving full play to by the function of the fail safe raising of perforated membrane generation, keeping the consideration of battery design capacity angle simultaneously, the thickness of perforated membrane is preferably 0.5～20 μ m.Under the situation that forms the perforated membrane that is made of multilayer film, the gross thickness of multilayer film also is preferably set to 0.5～20 μ m.In addition, the summation of membrane thicknesses and perforated membrane thickness is preferably 10～50 μ m, more preferably 10～30 μ m.

The battery that the present invention and then go for does not reel anodal and negative pole as described above, just is laminated.The thickness of perforated membrane is identical with convoluted battery.

Barrier film requires to be made of the material that can tolerate the lithium rechargeable battery environment for use.As such material, for example normally used is the microporous barrier that the vistanex by polyethylene, polypropylene etc. constitutes, but not special the qualification.Microporous barrier can be the monofilm that a kind of vistanex constitutes, and also can be the multilayer film that two or more vistanexes constitute.

Can embed/the anodal of removal lithium embedded ion be made of anodal core and appendix anode mixture thereon usually.Anode mixture generally contains positive active material, adhesive and conductive agent.

Composite oxides can be used for positive active material.As composite oxides, cobalt acid lithium (LiCoO preferably ₂), modifier, the lithium nickelate (LiNiO of cobalt acid lithium ₂), the modifier of lithium nickelate, LiMn2O4 (LiMn ₂O ₄), the modifier of LiMn2O4 etc.In various modifiers, often contain elements such as aluminium, magnesium.In addition, at least 2 kinds composite oxides that comprise among cobalt, nickel, the manganese are also arranged.

The adhesive that anode mixture contained for example can use polytetrafluoroethylene, modified propylene nitrile rubber particle, Kynoar etc., but there is no particular limitation.Polytetrafluoroethylene and modified propylene nitrile rubber particle preferably are used in combination with the carboxymethyl cellulose of the tackifier that become anode mixture raw material paste, poly(ethylene oxide), modified propylene nitrile rubber etc.Single Kynoar has the dual-use function of adhesive and tackifier.

Can insert/take off the negative pole of inserting lithium ion is made of negative pole core and appendix cathode agent thereon usually.Cathode agent generally contains negative electrode active material and adhesive, also contains conductive agent etc. as required.

Negative electrode active material for example can use material with carbon elements such as various native graphites, various Delanium, amorphous carbon, and silicide etc. contain silicon composite, various alloy materials etc.

The adhesive that cathode agent contained can use modifier, butadiene-styrene rubber, fluororesin, celluosic resin of Kynoar, Kynoar etc.

The conductive agent that is contained in anode mixture and the cathode agent can use carbon black, various graphite etc. such as acetylene carbon black, section's qin carbon black.

Nonaqueous electrolytic solution generally is made of nonaqueous solvents and the lithium salts that is dissolved in wherein.In nonaqueous electrolytic solution,, preferably contain vinylene carbonate, cyclohexyl benzene, diphenyl ether etc. as additive.

As nonaqueous solvents, can list ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propene carbonate, gamma-butyrolacton and derivative thereof etc.Their two or more uses of combination usually.

As lithium salts, for example can use phosphorus hexafluoride acid lithium (LiPF ₆), tetrafluoride lithium borate (LiBF ₄) etc.

Carry out specific description based on embodiment with regard to the present invention below, but following embodiment does not limit the present invention.

Embodiment 1

Describe below with reference to Fig. 2 and Fig. 3.

(i) Zheng Ji making

LiCoO with respect to 100 weight portions ₂, add 4 parts by weight of polyvinylidene fluoride (PVDF) as the acetylene carbon black of adhesive and 3 weight portions as conductive agent, add again an amount of NMP (N-N-methyl-2-2-pyrrolidone N-) carry out mixing, thereby mix the anode mixture paste.

Is the two sides of the aluminium foil core 21 of 20 μ m with the anode mixture paste coating that obtains at thickness, rolls the active material density (LiCoO that makes in the anode mixture 22 ₂Density) be 3.3g/ml, with it as anodal 23.The positive wire 24 that on anodal 23, connects aluminum.

The (ii) making of negative pole

Spherical Delanium with respect to 100 weight portions, styrene-methacrylic acid-the butadiene copolymer that adds 1 weight portion as the carboxymethyl cellulose of adhesive and 1 weight portion as tackifier, add again an amount of water carry out mixing, thereby mix the cathode agent paste.

Here, as the styrene-methacrylic acid-butadiene copolymer of adhesive, the BM400B that uses Japanese ZEON (strain) to produce.

Is the single face of the Copper Foil core 25 of 15 μ m with the cathode agent paste coating that obtains at thickness, and rolling the active material density (density of graphite) that makes in the cathode agent 26 is 1.4g/ml, with it as negative pole 27.On negative pole 27, connect negative wire 28 made of copper.

The (iii) formation of perforated membrane

Press table 1 and the mixed raw material shown in the table 2, mix the raw material paste of perforated membrane.Raw material in the paste (total amount of filler and resin binder) content all is set at 50 weight % in any case.

In resin binder, contain under the situation of BM500B, filler and resin binder are disperseed or make it to be dissolved in carry out among the NMP mixing, thereby mix the raw material paste.

Contain at resin binder under the situation of AD-211, filler and resin binder are disperseed or make it to dissolve carry out in the water mixing, thereby mix the raw material paste.

Then the single face applied thickness at negative pole 27 is the raw material paste of the perforated membrane of 20 μ m, so that cathode agent 26 is covered fully, thereby forms perforated membrane 31.Then, observe the outward appearance of perforated membrane, confirm whether to have the existence of peeling off.

Table 1

Embodiment	Amount (weight portion) with respect to the resin binder of per 100 weight portion fillers		The average grain diameter of filler (μ m)		Peeling off of perforated membrane	High-rate characteristics (%)	Be up to Da Wendu (℃)
								BM500B	PVDF	Aluminium oxide a	Aluminium oxide b
	A1	2	2	0.4								-	Do not have	86.3	167
B1					0.75	0.75	0.4	-	Do not have	89.9	165
	Compare battery 1a	0.5	0.5	0.4								-	Have	-	166
C1					3	3	0.4	-	Do not have	84.1	167
	D1	4	4	0.4								-	Do not have	80.5	169
Compare battery 2a					5	5	0.4	-	Do not have	73.8	165
	E1	2	2	0.4								0.05(B/A＝0.125)	Do not have	87.8	166
F1					2	2	0.4	0.02(B/A＝0.05)	Do not have	88.8	169
	G1	2	2	0.4								0.01(B/A＝0.025)	A little	89.2	168
H1					2	2	0.4	0.1(B/A＝0.25)	Do not have	86.6	163
	I1	2	2	0.4								0.15(B/A＝0.375)	Do not have	85.1	166
J1					2	2	0.2	-	A little	85.8	164
	K1	2	2	1								-	Do not have	86.4	166
L1					2	2	2	-	Do not have	86.7	168
	M1	0.8	3.2	0.4								-	A little	85.6	172
N1					3.2	0.8	0.4	-	Do not have	85.5	166
	Compare battery 3a	Microporous barrier										-	-	88.7	188
O1					2	2	0.1	-	A little	89.4	168
	P1	2	2	5								-	Do not have	81.6	168

Table 2

Embodiment	Amount (weight portion) with respect to the resin binder of per 100 weight portion fillers		The average grain diameter of filler (μ m)		Peeling off of perforated membrane	High-rate characteristics (%)	Be up to Da Wendu (℃)
								AD-211	CMC	Aluminium oxide a	Aluminium oxide b
	Q1	2	2	0.4								-	Do not have	86.4	166
R1					0.75	0.75	0.4	-	Do not have	89.7	165
	S1	4	4	0.4								-	Do not have	83.8	168

Describe with regard to raw material below.

[resin binder]

Resin binder also is 350,000 Kynoar (PVDF) or carboxymethyl cellulose (CMC) with core-shell rubber particles and molecular weight.

Here, to use the rubber particles that is made of AN-AE respectively be BM500B or the AD-211 that Japanese ZEON (strain) produces to the core-shell rubber particles.The average grain diameter of rubber particles is 0.2 μ m.

The absorption spectrum of measuring the rubber particles (BM500B) obtain with FT-IR as shown in Figure 6.Micro-FT-IR (Continu μ m type, light source: AVATAR-360) that determinator uses Nicolet company to produce.

The condition determination that sets is as follows: number of sample scan 32; Background scanning times 32; Resolution capability 4000; Sample gain 1.0.In addition, employed mensuration is as follows with method of sample preparation: rubber particles is dispersed among the NMP, is coated in then on the KBr plate, carry out drying then.

Among Fig. 6, in 2240cm ^-1Near the absworption peak seen be based on the stretching vibration peak of the C ≡ N of acrylonitrile, in 1733cm ^-1Near the absworption peak seen be based on the stretching vibration peak of C=O.In Fig. 6, be about 10 times based on the absorption peak strength (peak height) of the C ≡ N stretching vibration of acrylonitrile unit based on the absorption peak strength (peak height) of the stretching vibration of C=O.

In addition, about rubber particles (AD-211), also obtained same FT-IR measurement result.

[filler]

That filler uses is Al ₂O ₃Here, using average grain diameter individually is the aluminium oxide a of 0.4 μ m, and perhaps using aluminium oxide a and average grain diameter is the mixture of the aluminium oxide b of 0.01～0.15 μ m.Aluminium oxide a in the mixture and the content of aluminium oxide b are set at 90 weight % and 10 weight % respectively.In addition, measured the particle size distribution of alumina mixture, the result observes the particle diameter peak respectively at 0.35 μ m and 0.2 μ m or following.

The (iv) assembling of battery

After this, as shown in Figure 2, configuration positive pole 23 on perforated membrane 31, thus constitute the cascade type monocell of forming by a pair of positive pole and negative pole.Employing covers this monocell by the exterior body 32 that the ironed plate of aluminium lamination constitutes, and after this injects nonaqueous electrolytic solution in exterior body.

Here, employed nonaqueous electrolytic solution is that the volume ratio at ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate is in 1: 1: 1 the mixed solvent, dissolving phosphorus hexafluoride acid lithium (LiPF ₆) to make its concentration be the solution of 1 mol.In addition, with respect to mixed solvent, in nonaqueous electrolytic solution, add the vinylene carbonate of 4 volume %.

The resin-sealing material 33 that then will cover positive wire 24 and the part of negative wire 28 is respectively to being positioned at the open end of exterior body 32, thereby the free end of each lead-in wire guided under the outside state, and it is airtight that exterior body 32 is able to.So just, finished lithium rechargeable battery shown in Figure 3, its theoretical capacity is 600mAh.

In addition, for comparison purpose, only use the barrier film (thickness is 20 μ m) that constitutes by common polyethene microporous membrane, in this case, produced battery similarly to replace perforated membrane.

(the vi) fail safe of battery

That is scheduled to discharges and recharges and after making each cell activation, charges to cell voltage and reach 4.2V under 120mA, is discharged to cell voltage again under 60mA and reaches 3V.Then carry out same charging, make each battery that is in charged state be warmed up to 160 ℃.Stop heating at 160 ℃ then, battery is hung in the air, and under such state, with thermocouple measurement heating movement after this.At this moment, the maximum temperature of each battery arrival is shown in table 1 and table 2.

(the vii) high-rate characteristics of battery

That is scheduled to discharges and recharges and after making each cell activation, charges to cell voltage and reach 4.2V under 120mA, is discharged to cell voltage again under 60mA and reaches 3V.Then carry out same charging, under 600mA, be discharged to cell voltage and reach 3V.The ratio of the discharge capacity the when discharge capacity when then, obtaining the 600mA discharge with percentage is discharged with respect to 60mA.Its result is shown in table 1 and table 2.

(viii) evaluation result

As shown in Table 1: the amount of the resin binder in perforated membrane produces on perforated membrane and peels off, thereby can not get having the perforated membrane of abundant intensity more after a little while.In addition, when resin binder was too much, speed characteristic just descended greatly.

On the other hand, with respect to the filler of per 100 weight portions, when the content with the resin binder in the perforated membrane is set at 1.5～8 weight portions, then can obtain sufficient fail safe and suitable high-rate characteristics.This shows that the mixed proportion of filler and resin binder is important.In addition, show that also resin binder keeping the conductibility of lithium ion, keeping and have suitable rerum natura aspect the porous film strength simultaneously.

Secondly also as can be known: along with the increase of aluminium oxide a with the ratio (B/A value) of the average grain diameter of aluminium oxide b, speed characteristic has the tendency that reduces gradually.On the other hand also as can be known: when the B/A value was too small, the porous film strength had the tendency of decline.

In addition, when the average grain diameter of filler is too small,, cause the resin binder deficiency, thereby can see having produces the tendency of peeling off on perforated membrane because its surface area increases.On the other hand, when the average grain diameter of filler is excessive, cause the resin binder surplus, thereby can see having the tendency that high-rate characteristics descends.

Embodiment 2

(i) making of positive pole and negative pole

Produce positive pole and negative pole similarly to Example 1.

The (ii) formation of perforated membrane

Allocate the raw material paste of perforated membrane similarly to Example 1.Here, in the ratio shown in the table 3, make filler and resin binder be dispersed among the NMP and carry out mixing, thereby mix the raw material paste of perforated membrane.The content of raw material in the paste (total amount of filler and resin binder) is under any circumstance all set 50 weight %.It is the aluminium oxide (Al of 0.4 μ m that filler uses average grain diameter separately ₂O ₃).

Table 3

Embodiment	Amount (weight portion) with respect to the resin binder of per 100 weight portion fillers		The average grain diameter of filler (μ m)	The average pore size (μ m) of micropore in the perforated membrane	Peeling off of perforated membrane	High-rate characteristics (%)
							BM500B	PVDF
	A2	0.75							0.75	0.4	0.05	Do not have	87.6
Compare battery 1b			0.5	0.5	0.4	0.05	Have	-
	B2	3							3	0.4	0.05	Do not have	84.1
C2			4	4	0.4	0.05	Do not have	80.9
	Compare battery 2b	5							5	0.4	0.05	Do not have	76.5
Compare battery 3b			2	2	0.4	0.01	Do not have	75.9
	D2	2							2	0.4	0.02	Do not have	84.0
E2			2	2	0.4	0.05	Do not have	86.1
	F2	2							2	0.4	0.07	Do not have	85.2
G2			2	2	0.4	0.09	Do not have	82.9
	Compare battery 4b	2							2	0.4	0.12	Do not have	77.0
H2			0.8	3.2	0.4	0.05	Do not have	85.8
	I2	3.2							0.8	0.4	0.05	Do not have	84.3
J2			2	2	0.2	0.05	A little	87.2
	K2	2							2	1	0.05	Do not have	82.9
L2			2	2	2	0.05	Do not have	80.8

Shown in Fig. 2,3, single face applied thickness at negative pole 27 is the raw material paste of the perforated membrane of 20 μ m, so that make it to cover fully cathode agent 26, the calender calendering is carried out with predetermined line pressure in dry back, thereby forms the perforated membrane 31 in the space with the average pore size shown in the table 3.Then, observe the outward appearance of perforated membrane, confirm whether to have the generation of peeling off.

The (iii) mensuration of average pore size

The average pore size in space adopts the bubble point method, and the pore measure of spread device (PermPorometer) that uses PMI company to produce is measured.When carrying out the mensuration of moistening flow W, employed solvent is a water.

Peel perforated membrane from the negative pole of making for pore size determination, also can obtain pore-size distribution with this film, but obtain the pore-size distribution of negative pole here in advance, obtain the pore-size distribution of the negative pole that forms perforated membrane again, obtain the just pore-size distribution of perforated membrane from both differences.Because the aperture in the space that negative pole had is generally 0.5～5 μ m, the aperture in the space that perforated membrane had is generally 0.02～0.09 μ m, so the pore-size distribution that will be perforated membrane easily extracts.

Specifically, at negative pole or be formed with the air pressure that adds on the negative pole sample of perforated membrane until 250Psi, obtain dry flow D.Then behind the abundant wetting sample of water, topped up with water in the container of placing sample adds the air pressure until 250Psi on sample, obtain moistening flow W.For any one sample, in 160～230Psi scope, the D value is consistent with the W value.

For each sample, the distribution of the flow percentage Q when obtaining value from the bubble point to D=W value.Deduct the distribution of negative pole from the distribution of the negative pole that is formed with perforated membrane, thereby the distribution of perforated membrane is extracted.So the intermediate value of the aperture d in the distribution that extracts is just as the average pore size in the space that perforated membrane had and obtain.

In addition, flow percentage Q is by giving a definition, and when D value=W value, the accumulated value of Q is 100%.

Q＝Δ(W/D)＝(Wh/Dh-Wl/Dl)×100

Wh: on high-tension side wetting flow (L/min of unit)

Wl: the wetting flow of low-pressure side (L/min of unit)

Dh: on high-tension side wetting flow (L/min of unit)

Dl: the wetting flow of low-pressure side (L/min of unit)

The (iv) assembling of battery

Except the perforated membrane that is controlled in the average pore size that forms the space that obtains on the negative pole, similarly to Example 1, produce lithium rechargeable battery shown in Figure 3, its theoretical capacity is 600mAh.

(the v) high-rate characteristics of battery

Estimated the high-rate characteristics in the battery similarly to Example 1.Its result is as shown in table 3.

(vi) evaluation result

From the result of table 3 also as can be known: the amount of the resin binder in perforated membrane produces on perforated membrane and peels off, thereby can not get having the perforated membrane of abundant intensity more after a little while.In addition, when resin binder is too much, cause that speed characteristic descends.That is to say that the result of table 3 shows:, should resin-bonding agent content in the perforated membrane be set at 1.5～8 weight portions with respect to the filler of per 100 weight portions in order to obtain good speed characteristic.

Secondly also as can be known: even under the amount of the resin binder that is contained in the perforated membrane situation identical with the average grain diameter of filler, the average pore size of perforated membrane internal pore is too small or excessive, all causes the decline of speed characteristic.That is to say that the result of table 3 shows:, the average pore size of micropore in the perforated membrane should be set at 0.02～0.09 μ m in order to obtain good speed characteristic.

In addition, when the average grain diameter of filler is too small, because its surface area increases, thus the resin binder deficiency, thus can see having on perforated membrane produces the tendency of peeling off.On the other hand, when the average grain diameter of filler is excessive, can see having the tendency that high-rate characteristics descends, it is generally acknowledged that its reason is the resin binder surplus, or can not get having the space that is suitable for the aperture that lithium ion moves.

Embodiment 3

(i) Zheng Ji making

Except with the pole plate dimension modifying for the predetermined size, produce positive pole similarly to Example 1.

The (ii) making of negative pole

At the two sides of Copper Foil core appendix cathode agent, make active material density (density of graphite) reach 1.4g/ml by calendering, the pole plate dimension modifying for predetermined ground size, in addition, is produced negative pole similarly to Example 1.

The (iii) formation of perforated membrane

In the ratio shown in the table 4, make filler and resin binder be dispersed among the NMP and carry out mixing, thereby mix the raw material paste of perforated membrane.The content of raw material in the paste (total amount of filler and resin binder) is under any circumstance all set 50 weight %.

Similarly to Example 1, to use average grain diameter separately be the aluminium oxide a of 0.4 μ m to filler or use aluminium oxide a and average grain diameter is the mixture of the aluminium oxide b of 0.01～0.15 μ m.Aluminium oxide a in the mixture and the content of aluminium oxide b are set at 90 weight % and 10 weight % respectively.

Be the raw material paste of the perforated membrane of 20 μ m then,, descended dry 20 minutes at 90 ℃ then, just form perforated membrane so that cathode agent is capped fully in the two sides of negative pole applied thickness.Then, observe the outward appearance of perforated membrane, confirm whether to have the generation of peeling off.

Table 4

Embodiment	Amount (weight portion) with respect to the resin binder of per 100 weight portion fillers		The average grain diameter of filler (μ m)		Peeling off of perforated membrane	The percentage elongation of perforated membrane (%)	Short circuit	High-rate characteristics (%)
									BM500B	PVDF	Aluminium oxide a	Aluminium oxide b
	A3	2	2	0.4									-	Do not have	18.6	Do not have	85.7
B3					3.2	0.8	0.4	-	Do not have	15.1	Do not have	88.0
	C3	0.75	0.75	0.4									-	Do not have	15.6	Do not have	89.2
D3					4	4	0.4	-	Do not have	20.8	Do not have	83.1
	E3	2	2	0.4									0.05 (B/A＝0.125)	Do not have	20.8	Do not have	87.5
F3					2	2	0.4	0.02 (B/A＝0.05)	Do not have	20.4	Do not have	88.4
	G3	2	2	0.4									0.1 (B/A＝0.25)	Do not have	19.5	Do not have	86.1
H3					0	4	0.4	-	Do not have	10.3	Have	-
	I3	0.5	0.5	0.4									-	Have	7.7	Have	-
J3					5	5	0.4	-	Do not have	19.8	Do not have	64.9
	K3	2	2	0.4									0.01 (B/A＝0.025)	Have	13.8	Have	-
L3					2	2	0.4	0.15 (B/A＝0.375)	Do not have	15.5	Do not have	82.3

The (iv) assembling of battery

Describe below with reference to Fig. 7.

With the surperficial bonding perforated membrane 310 of negative pole 270 on configuration anodal 230, integral body is reeled, just obtain cylindrical shape pole plate group.Dead ring 310a of configuration up and down and 310b in this pole plate group insert in the battery can 290 made of iron then.Then positive wire 240 and negative wire 280 are welded on the inboard of hush panel 300 and the inner bottom surface of battery can respectively.After this, in battery can, inject nonaqueous electrolytic solution, last, get involved packing ring 320, make the periphery ca(u)lk of the open end of battery can in hush panel 300.Employed nonaqueous electrolytic solution is identical with embodiment 1.

Like this, (18650: the cylindrical shape of diameter 18mm, height 65mm), its theoretical capacity is 2000mAh just to produce lithium rechargeable battery shown in Figure 7.

(the v) percentage elongation of perforated membrane

The percentage elongation of perforated membrane is measured according to JIS C2318 and by following main points.

At first, on the film that PETG (PET) is made, applied thickness is the employed perforated membrane raw material of each battery paste of 20 μ m, and following dry 20 minutes in 90 ℃.After this, from the PET film, dried perforated membrane is stripped down, and the perforated membrane that obtains is cut into the size of 15mm * 25mm, it is measured as percentage elongation use sample.

Percentage elongation measured be installed on the predetermined cupping machine with sample, the draw speed that can obtain the elongation of 5mm with per minute is tested then.Elongation during then, with sample fracture is obtained percentage elongation with respect to the ratio (%) of specimen length (25mm).Its result is as shown in table 4.

(vi) short circuit has or not

For making the battery of finishing after sealing, discharge and recharge in advance by pattern shown below, and under 45 ℃ environment, preserved 7 days.

Constant current charge: 400mA (final voltage 4.0V)

Constant current discharge: 400mA (final voltage 3.0V)

Constant current charge: 400mA (final voltage 4.0V)

Constant current discharge: 400mA (final voltage 3.0V)

Constant current charge: 400mA (final voltage 4.0V)

In the front and back of carrying out above-mentioned preservation, measure the voltage of each battery, the external voltage after preserving is reduced to the generation that 70mV or above battery are judged as short circuit.Its result is as shown in table 4.

(the vii) high-rate characteristics of battery

At 45 ℃ of qualified batteries that do not have short circuit to take place after preserving 7 days down, after this under 20 ℃ environment, carry out discharging and recharging of following pattern to above-mentioned.

(1) discharge in advance

Constant current discharge: 400mA (final voltage 3.0V)

(2) the 1st patterns

Constant current charge: 1400mA (final voltage 4.2V)

Constant voltage charging: 4.2V (stopping electric current 100mA)

Constant current discharge: 400mA (final voltage 3.0V)

(3) the 2nd patterns

Constant current charge: 1400mA (final voltage 4.2V)

Constant voltage charging: 4.2V (stopping electric current 100mA)

Constant current discharge: 4000mA (final voltage 3.0V)

The ratio of the discharge capacity the when discharge capacity when then, obtaining the 4000mA discharge with percentage is discharged with respect to 400mA.Its result is as shown in table 4.

(viii) evaluation result

As shown in Table 4: the amount of the resin binder in perforated membrane just produces at perforated membrane and to peel off more after a little while, can not get having the perforated membrane of abundant percentage elongation.In addition also as can be known: when resin binder was too much, high-rate characteristics just descended greatly.That is to say that the result of table 4 also shows:, the resin-bonding agent content in the perforated membrane should be set at 1.5～8 weight portions with respect to the filler of per 100 weight portions.In addition also as can be known: the percentage elongation of perforated membrane is lower than at 15% o'clock, and the possibility that is short-circuited increases.

Secondly also as can be known:, have the tendency that percentage elongation reduces, high-rate characteristics descends gradually of perforated membrane along with the increase of aluminium oxide a with the ratio (B/A value) of the average grain diameter of aluminium oxide b.On the other hand also as can be known: when the B/A value was too small, the percentage elongation of perforated membrane had the tendency of decline.

Embodiment 4

Battery 1～7

(i) Zheng Ji making

#1320 (nmp solution that contains 12 weight % Kynoar), 90g acetylene carbon black and an amount of NMP that 3kg cobalt acid lithium, 1kg are produced as the Wu Yu chemistry (strain) of adhesive stir with double arm kneading mixer (double-arm kneader), just mix the anode mixture paste.This paste of coating rolls after the drying on the thick aluminium foil of 15 μ m, just forms the anode mixture layer.At this moment, will be set at 160 μ m by the electrode thickness that aluminium foil and mixture layer constitute.After this, pole plate is cut into a certain width, so as enabling to insert diameter to be 18mm, highly in the battery case for the size of 65mm, thereby obtain anodal band (hoop).

The (ii) making of negative pole

3kg Delanium, 75g are stirred with double arm kneading mixer as the carboxymethyl cellulose of tackifier and an amount of water as BM-400B (aqueous liquid dispersion that contains 40 weight % Styrene-Butadiene), the 30g of Japanese ZEON (strain) production of adhesive, just mix the cathode agent paste.This paste of coating rolls after the drying on the thick Copper Foil of 10 μ m, just forms anode mixture layer.At this moment, will be set at 180 μ m by the electrode thickness that Copper Foil and mixture layer constitute.After this, pole plate is cut into the width that can insert in the above-mentioned battery case, just obtains the negative pole band.

The (iii) formation of perforated membrane

In battery 1～7, on negative pole, make 1 layer of perforated membrane.

The aluminium oxide, 500g that adds 960g and as the median particle diameter of inorganic oxide filler be 0.3 μ m in double arm kneading mixer stirs with an amount of NMP as the modified propylene nitrile rubber (BM-720H, solid constituent that Japanese ZEON (strain) produces are 8 weight %, NMP 92 weight %) of adhesive, just mixes the raw material paste of perforated membrane.Apply this paste on the two sides of negative pole, carry out drying, just form the perforated membrane that thickness is 6 μ m with the drying condition shown in the table 5.

The (iv) assembling of battery

Coiling is by barrier film positive pole of separating and the negative pole with perforated membrane, and in the insertion battery case, the thickness of wherein said barrier film is 20 μ m, is made of the polyethylene microporous membrane.Then weighing 5.5g nonaqueous electrolytic solution is injected in the battery case, and the peristome to shell seals then.Like this, just, produce columnar lithium rechargeable battery.

Here, employed nonaqueous electrolytic solution is that the volume ratio at ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate is in 2: 3: 3 the mixed solvent, dissolving phosphorus hexafluoride acid lithium (LiPF ₆) to make its concentration be the solution of 1 mol.In addition, with respect to nonaqueous electrolytic solution, added the vinylene carbonate of 3 weight %.

Battery 8

Except making by following main points on the negative pole 2 layers of perforated membrane, similarly make battery 8 with battery 1.

In double arm kneading mixer, add 990g and battery 1 same aluminium oxide, 125g and stir, just mix the raw material paste of perforated membrane as the BM-720H of adhesive and an amount of NMP.Apply this paste on the two sides of negative pole, and 90 ℃ of following dry 10 seconds, just producing thickness is the 1st layer of perforated membrane of 4 μ m.

Then in double arm kneading mixer, add 980g and battery 1 same aluminium oxide, 250g and stir, just allocate the raw material paste of perforated membrane as the BM-720H of adhesive and an amount of NMP.This paste of coating on the 1st layer of perforated membrane, and 90 ℃ of following dry 10 seconds, just forming thickness is the 2nd layer of perforated membrane of 2 μ m.

Battery 9

Except making by following main points on the negative pole 2 layers of perforated membrane, similarly make battery 9 with battery 1.

At first, similarly form the 1st layer of perforated membrane with battery 8.After this, the perforated membrane raw material paste that constitutes as the BM-720H of adhesive and an amount of NMP by the same aluminium oxide of 900g and battery 1,1250g of allotment.This paste of coating on the 1st layer of perforated membrane, and 90 ℃ of following dry 10 seconds, just forming thickness is the 2nd layer of perforated membrane of 2 μ m.

Battery 10

Except making by following main points on the negative pole 2 layers of perforated membrane, similarly make battery 10 with battery 1.

At first, similarly form the 1st layer of perforated membrane with battery 8.After this, the perforated membrane raw material paste that constitutes as the BM-720H of adhesive and an amount of NMP by the same aluminium oxide of 700g and battery 1,3750g of allotment.This paste of coating on the 1st layer of perforated membrane, and 90 ℃ of following dry 10 seconds, just forming thickness is the 2nd layer of perforated membrane of 2 μ m.

Battery 11

Except making by following main points on the negative pole 2 layers of perforated membrane, similarly make battery 11 with battery 1.

At first, similarly form the 1st layer of perforated membrane with battery 8.After this, the perforated membrane raw material paste that constitutes as the BM-720H of adhesive and an amount of NMP by the same aluminium oxide of 600g and battery 1,5000g of allotment.This paste of coating on the 1st layer of perforated membrane, and 90 ℃ of following dry 10 seconds, just forming thickness is the 2nd layer of perforated membrane of 2 μ m.

Battery 12

As the inorganic oxide filler, use titanium oxide to replace aluminium oxide, in addition, similarly make battery 12 with battery 9.

Battery 13

As adhesive, use PVDF to replace BM-720H, in addition, similarly make battery 13 with battery 9.

Compare battery 1

Except stacked 2 layers of the 1st layer of perforated membrane that perforated membrane is same with battery 8 on the negative pole, similarly make relatively battery 1 with battery 1.

Compare battery 2

As filler, use polyethylene (PE) system bead to replace beyond the aluminium oxide, similarly make relatively battery 2 with battery 9.

Compare battery 3

Except not forming on the negative pole the perforated membrane, similarly make relatively battery 3 with battery 1.

(v) porous film strength

About the above-mentioned negative pole except that the negative pole of battery 3 relatively, serve as the negative pole that the axle coiling has perforated membrane with the pole of Φ 5mm, the cracking situation of observing perforated membrane and negative pole then.On perforated membrane and negative pole, do not observe defective, crackle and be designated as " OK " when coming off, be designated as " NG " when observing.Its result is as shown in table 5.In addition, the structure condition of each battery is also illustrated in the table 5.In addition, when the intensity of perforated membrane and negative pole is " NG ", then end the making of battery.

(vi) flash-over characteristic

Battery about making discharges and recharges in advance by pattern shown below, and preserves 7 days under 45 ℃ environment.

Constant current charge: 400mA (final voltage 4.0V)

Constant current discharge: 400mA (final voltage 3.0V)

Constant current charge: 400mA (final voltage 4.0V)

Constant current discharge: 400mA (final voltage 3.0V)

Constant current charge: 400mA (final voltage 4.0V)

After this, under 20 ℃ environment, carry out discharging and recharging of following pattern.

(1) discharge in advance

Constant current discharge: 400mA (final voltage 3.0V)

(2) the 1st patterns

Constant current charge: 1400mA (final voltage 4.2V)

Constant voltage charging: 4.2V (stopping electric current 100mA)

Constant current discharge: 400mA (final voltage 3.0V)

(3) the 2nd patterns

Constant current charge: 1400mA (final voltage 4.2V)

Constant voltage charging: 4.2V (stopping electric current 100mA)

Constant current discharge: 4000mA (final voltage 3.0V)

At this moment, the result of discharge capacity is as shown in table 5.

(vii) nail thorn test

To flash-over characteristic evaluation battery later, carry out following charging.

Constant current charge: 1400mA (final voltage 4.25V)

Constant voltage charging: 4.25V (stopping electric current 100mA)

For the battery after the charging, under 20 ℃ environment, from its side and it is pricked with the iron wire nail of Φ 2.7mm with the speed of 5mm/ second saturating, the febrile state of observation this moment then.It is as shown in table 5 in the result of the arrival temperature after with 90 seconds after 1 second that battery is pricked the position.

Table 5

Embodiment	Perforated membrane					Baking temperature (℃)	Drying time (second)	Perforated membrane intensity	Flash-over characteristic		The test of nail thorn
													Layer structure	Filler			Binding agent	Discharge capacity (mAh)		Be up to Da Wendu (℃)
	Kind	The 1st layer of content (%)	The 2nd layer of content (%)	Kind	400mA				4000mA	After 1 second	After 90 seconds
												1		1 layer	Aluminium oxide	96		BM-720H	100	10	OK	2010	1869	63	88
2	120	OK	2012	1891	64	87
							3	140	OK	2013	1882	64	86
4	160	OK	2013	1852	63	89
							5	180	OK	2012	1831	62	88
6	200	OK	2009	1811	77	104
							7	90	OK	2010	1790	75	102
8	2 layers	99	98	OK	2011	1890													65		89
							9		99	90	OK	2010	1829	64		87
10		99	70	OK	2012	1790											63		88
							11		99	60	OK	2009	1740	69		88
12		Titanium oxide	99	90	OK	2013											1832		71		90
							13		Aluminium oxide	99	90	PVDF	OK	2009	1859	72						146
Compare battery 1d		99	99	BM-720H	NG	Do not estimate											Do not estimate	Do not estimate	Do not estimate
							Compare battery 2d			The PE bead	99	90	OK	2012	1851	146					Do not estimate
Compare battery 3d		Do not have	Do not have		Do not have	Do not have			Do not have								Do not have	Do not have	Do not estimate			2012	1710	146	Do not estimate

(viii) evaluation result

As battery 1～7, under 90～200 ℃ baking temperature, when on negative pole, only forming 1 layer of aluminium oxide and account for the perforated membrane of 96 weight %, to compare with battery 1 relatively, porous film strength, flash-over characteristic, the test of nail thorn can obtain good result.In addition, also be good even the flash-over characteristic of battery 1～7 is compared with comparison battery 3.

Battery 6 when baking temperature is 200 ℃ is compared with battery 1～5, and aspect the flash-over characteristic under constant current 4000mA, its discharge capacity is lower, even aspect the test of nail thorn, the arrival temperature after 90 seconds is also higher.Battery 7 when baking temperature is 90 ℃ is compared with battery 1～5, and aspect the test of nail thorn, the arrival temperature after 90 seconds is higher.

So, analyzed alumina content at the perforated membrane thickness direction with regard to battery 1～7.By its result as can be known: when baking temperature was higher, the alumina content of porous film surface side reduced, and adhesive increases.Special is the situation of 200 ℃ battery 6 for baking temperature, and the alumina content of porous film surface side is 60 weight %.It is generally acknowledged one to 200 ℃ of baking temperature, because the adhesive of porous film surface side increases, so the absorbency of electrolyte is hindered, so that flash-over characteristic descends.

In addition, be the situation of 90 ℃ battery 7 for baking temperature, the alumina content of porous film surface side is 95.5 weight %, and is very nearly the same with the content of aluminium oxide in whole perforated membrane of 96 weight %.Therefore, the difference of the filer content of porous film surface side and the filler content in whole perforated membrane be preferably set to 1 weight % or more than.In addition, consider that from the flash-over characteristic and the angle of nail thorn test the baking temperature when forming 1 layer of perforated membrane on electrode is preferably set to 100～180 ℃.

As battery 8～11, when in 60～98 weight % scopes, changing the alumina content of the 2nd layer of perforated membrane, compare with 3 with comparing battery 1, aspect porous film strength, flash-over characteristic or the test of nail thorn, can obtain good result.Battery 11 is compared with battery 8～10, and aspect the flash-over characteristic under constant current 4000mA, its discharge capacity is lower.It is generally acknowledged that its reason is: because the adhesive of the 2nd layer of perforated membrane is more, thereby can not fully guarantee the gap between the filler, so that electrolyte becomes insufficient to the supply of electrode.

In addition, as comparing battery 1, when 2 layers of aluminium oxide of formation were the perforated membrane of 99 weight % on negative pole, in the strength test of the perforated membrane that is undertaken by coiling, because observe coming off of cathode agent, so that battery can not be made.Therefore, consider that from two angles of perforated membrane intensity and flash-over characteristic the inorganic oxide filler is preferably the scope of 70～98 weight % in the shared ratio of porous film surface side.

As comparing battery 2, when using PE system bead, the result that the nail thorn is tested is identical with the situation that does not have perforated membrane.This shows when using thermal endurance and barrier film to be the filler of microporous barrier equal extent, can not give play to the desired effect of the present invention.Therefore, filler must be selected inorganic oxide.

As battery 12, when using titanium oxide to replace aluminium oxide, can confirm to have same effect with aluminium oxide.Hence one can see that, and the inorganic oxide filler beyond the aluminium oxide also is operable.

As battery 13, when the perforated membrane that uses adhesive to constitute by PVDF, in the test of nail thorn, the arrival temperature after 1 second and other embodiment much at one, but the rising of the arrival temperature after 90 seconds.The result who decomposes this battery can confirm the existence of perforated membrane, but compares with battery 1～12, and short position enlarges.Hence one can see that, as the adhesive of perforated membrane, preferably is difficult to take place the adhesive with fusion of burning of adhesive itself, and specifically, preferred temperature of initial decomposition is that 250 ℃ or above, crystalline melting point are 250 ℃ or above adhesive.Amorphism macromolecule acrylonitrile unit, that have the rubber proterties that for example preferably will contain temperature of initial decomposition and be 320 ℃ is as adhesive.

As battery 3 relatively, when not having perforated membrane, with battery 1～13 and relatively battery 1 situation that on electrode, forms perforated membrane like that compare, the arrival temperature after 1 second raises.After the test, with the result that these batteries decompose, compare the battery of battery 3, fusion is taking place in the scope in barrier film widely.In contrast, battery 1～13 is present on the electrode with the battery that compares battery 1, the former state that its perforated membrane shines when making, and the thermal contraction of barrier film also is suppressed.Can think thus: by using the perforated membrane that constitutes by the high adhesive of melt temperature, even the short circuit during because of the nail thorn produces heating, perforated membrane can not destroyed yet, and can suppress the expansion of the heating position that caused by short circuit, thereby thermal runaway is prevented.

Here, feature and the data interpretation that just substitutes the nail thorn test of evaluation as internal short-circuit is described in detail.At first,, produce the reason of heating, can be explained as follows about the nail thorn according to the experimental result in past.

When the effect owing to nail thorn make anodal when partly contacting (short circuit) with negative pole, short circuit current flow and produce Joule heat right over there.Then, under the effect of Joule heat, the diaphragm material generation fusion that thermal endurance is low causes short position to enlarge.Its result, Joule heat continues to produce, and barrier film enlarges because of thermal contraction makes its defect.Like this, positive pole is raised to heat-labile temperature province (160 ℃ or more than).Cause the generation of thermal runaway like this.

In addition, embodiment is illustrated with regard to the situation that forms perforated membrane on the negative pole, but no matter forming on the positive pole or forming on the two poles of the earth, can obtain same result.In addition, embodiment is illustrated with regard to the situation that forms 1 layer or 2 layers perforated membrane on the negative pole, but also can be 3 layers or more multi-layered, can obtain the effect same with embodiment.

For require to have fail safe, good charge-discharge characteristic and the lithium rechargeable battery of high-rate characteristics, the present invention is exceedingly useful in the field of this lithium rechargeable battery.Lithium rechargeable battery of the present invention can be used as the driving power of the electronic equipment of notebook computer, mobile phone, digital camera etc.

Claims (15)

1. lithium rechargeable battery, it constitutes: can embed/positive pole of removal lithium embedded ion, can insert/take off the negative pole of inserting lithium ion, perforated membrane between described positive pole and negative pole and nonaqueous electrolytic solution; At least one side's of wherein said perforated membrane and described positive pole and negative pole is surperficial bonding; Described perforated membrane is made of filler and resin binder; The content of described resin binder in described perforated membrane is that the described filler with respect to per 100 weight portions is 1.5～8 weight portions; Described resin binder contains acrylonitrile unit, acrylic ester unit or methacrylate unit.

2. lithium rechargeable battery according to claim 1, wherein the average pore size of micropore is 0.02～0.09 μ m in the described perforated membrane of being tried to achieve by the bubble point method.

3. lithium rechargeable battery according to claim 1, the percentage elongation of wherein said perforated membrane be 15% or more than.

4. lithium rechargeable battery according to claim 1, the amount of wherein said resin binder, less in the 1st face side that described perforated membrane and described electrode surface are bonding, more in the 2nd face side of the relative side on described the 1st surface.

5. lithium rechargeable battery according to claim 1, wherein said filler is made of the mixture of macroparticle group and small-particle group, and the average grain diameter B of the average grain diameter A of described macroparticle group and described small-particle group satisfies formula (1): 0.05≤B/A≤0.25.

6. lithium rechargeable battery according to claim 1, wherein said resin binder is made of the core-shell rubber particles, and described rubber particles has the adhesiveness skin section.

7. lithium rechargeable battery according to claim 1, wherein said filler contains Al at least ₂O ₃

8. lithium rechargeable battery according to claim 1, wherein said resin binder have 250 ℃ or above temperature of initial decomposition.

9. lithium rechargeable battery according to claim 8, wherein said resin binder have 250 ℃ or above crystalline melting point.

10. lithium rechargeable battery according to claim 4, wherein said perforated membrane is made of 1 tunic, and the amount of described resin binder increases gradually from described the 2nd face side of described the 1st surface lateral.

11. lithium rechargeable battery according to claim 4, wherein said perforated membrane is made of multilayer film, and the described resin binder that is arranged in the film of described the 2nd face side is arranged in the described resin binder of film of described the 1st face side at the shared ratio height of the total amount of described filler and described resin binder at the shared ratio of the total amount of described filler and described resin binder.

12. lithium rechargeable battery according to claim 4, wherein in the skin section of described the 2nd face side of described perforated membrane, described filler shared ratio in the total amount of described filler and described resin binder is 70～98 weight %, and the thickness of described skin section is 20% of described perforated membrane thickness.

13. lithium rechargeable battery according to claim 1, wherein said positive pole and described negative pole are wound into helical form in the mode across described perforated membrane only.

14. lithium rechargeable battery according to claim 1, wherein said positive pole and described negative pole are wound into helical form in the mode across described perforated membrane and barrier film.

15. the manufacture method of the described lithium particle secondary cell of claim 1, it has following operation: (a) the allotment paste makes it to contain: the filler of 100 weight portions, 1.5 the resin binder that contains acrylonitrile unit, acrylic ester unit or methacrylate unit of～8 weight portions, and the decentralized medium of described filler; (b) with described paste coating at least one side's of anodal and negative pole surface; (c) under 100 ℃～180 ℃ temperature, the paste that is coated in described electrode surface is carried out drying.

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