CN101061601A - Lithium secondary battery - Google Patents
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- CN101061601A CN101061601A CNA2006800011743A CN200680001174A CN101061601A CN 101061601 A CN101061601 A CN 101061601A CN A2006800011743 A CNA2006800011743 A CN A2006800011743A CN 200680001174 A CN200680001174 A CN 200680001174A CN 101061601 A CN101061601 A CN 101061601A
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Abstract
A lithium secondary battery that is excellent in resistance to short-circuits and heat, is unlikely to suffer a capacity loss due to impact such as dropping, and has a high capacity. The lithium secondary battery includes: an electrode assembly including a strip-like positive electrode and a strip-like negative electrode that are wound together with a porous heat-resistant layer interposed therebetween; a non-aqueous electrolyte; and a battery can. The battery has a restricting part for restricting vertical movement of the electrode assembly. The distance A from the restricting part to the inner bottom face of the battery can and the width B of the negative electrode satisfy the relation: 0.965<=B/A<=0.995.
Description
Technical field
The present invention relates to a kind of higher lithium secondary batteries of safety with outstanding resistance to shorting and heat resistance.The present invention is more particularly directed to a kind of for generating the technology of capacitance loss due to preventing battery from such as falling because impacting.
Background technique
Lithium secondary battery has attracted attention as the high-capacity power supply of mancarried device and other devices.In addition, lithium secondary battery is recently also of increasing concern as the high output power of electric vehicle etc..Chemical cell such as lithium secondary battery usually has the diaphragm that positive electrode and negative electrode can be made to be electrically insulated and keep electrolyte.In the lithium secondary battery, mainly the microporous barrier made of polyolefin (such as polyethylene, polypropylene etc.) makees diaphragm.By the way that the diaphragm between anode and cathode and two electrodes of insertion is intertwined, the electrode assembly of lithium secondary battery may be produced that cylindrical or substantially elliptical cylinder.
Cylindrical lithium secondary battery can be used as, for example, the power supply of power tool and laptop.Cylindrical lithium secondary battery can be sealed by the way that the opening edge of its battery case to be crimped on sealing plate.To make sealing plate be fixed on the open-topped periphery of battery case, the step (narrow) that battery case has an internal diameter to reduce in the upper half of its side wall.Patent document 1 proposes a kind of high capacity design, and the width B (38mm) of cathode meets relational expression with from narrow to battery case outer bottom distance A (39.7mm) in the design: B/A=0.957.
Prismatic lithium secondary battery can be used as, for example, the power supply of portable phone and digital still camera.Since prismatic lithium secondary battery is easier to be installed into device than cylindrical, they just become to become increasingly popular.In prismatic lithium secondary battery, connection electrode is easy to contact with battery case with the lead of terminal, this is different from cylindrical lithium secondary battery.Short circuit can occur when the wire contacts opposite with battery case when polarity are to battery case.Therefore insulator (hereinafter referred to as upper portion insulating body) is set usually between the upper half of electrode assembly and the lid (insulation board) of battery case.To further increase resistance to shorting, people are it is also proposed that be arranged insulator (hereinafter referred to as lower isolator) (patent document 2) between the lower half of electrode assembly and the bottom of battery case.
The electrode assembly of prismatic lithium secondary battery, which is typically made into from the lower surface of upper portion insulating body, meets relational expression the distance A to battery case inner bottom surface and the width B of cathode: B/A≤0.96.The ratio of B/A is higher, and battery capacity is higher.However, electrode assembly can be sensitive to distortion, directly contacts so as to cause between anode and cathode, i.e., short-circuit if the ratio of B/A is excessively high.In patent document 2, by being arranged as the lower isolator of buffer, the ratio of B/A is set as high as 0.97.
Meanwhile when lithium secondary battery long-time preservation under thermal extremes environment, the diaphragm made of microporous barrier has tendencies toward shrinkage.If diaphragm retracts, anode and cathode can actually be in contact with each other to generate internal short-circuit.In view of recent development trend is the capacity for keeping diaphragm thinning while increasing lithium secondary battery, therefore prevent internal short-circuit from becoming to be even more important.Once internal short-circuit occurs, short circuit can expand because of the Joule heat of short circuit current generation, so as to cause battery overheat.
Therefore, it when internal short-circuit occurs, to inhibit this kind of short circuit to expand, proposes to form the porous heat-resistant layer for containing inorganic filler (fine solid particle) and adhesive in electrode active material layers.Aluminium oxide, silica etc. can be used as inorganic filler.Inorganic filler is filled out in porous heat-resistant layer, and the adhesive of filler grain relatively small amount herein is bonded to one another (patent document 3).Even if since porous heat-resistant layer all has anti-contracility at high temperature, therefore it plays the role of inhibiting battery overheat under internal short-circuit.
Patent document 1: the flat 11-354084 of Japanese patent application No..
Patent document 2: Japanese patent application No.2004-31263.
Patent document 3: the flat 7-220759 of Japanese patent application No..
Summary of the invention
The problem to be solved in the present invention
In order to realize the lithium secondary battery with high capacity and outstanding resistance to shorting, use can the proposal of patent document 1 or patent document 2 be combined with the proposal of patent document 3.This combination considerably reduces internal short-circuit, but when battery is impacted, and when such as falling, will lead to apparent capacitance loss.
In view of the above problem, an object of the present invention is to provide a kind of with outstanding resistance to shorting, the lithium secondary battery that can be prevented capacitance loss caused by falling and can be carried out high capacity design.
Solution to the problem
The present invention relates to a kind of lithium secondary batteries comprising: there is bottom, side wall and open-topped battery case；Electrode assembly；Nonaqueous electrolytic solution；And open-topped sealing plate of the covering to the battery case of accommodate electrod component and electrolyte.Electrode assembly includes the bar shaped anode and bar shaped cathode being intertwined with the porous heat-resistant layer of insertion between a positive electrode and a negative electrode.Anode includes positive core components and the anode active material layer that is coated on the core components, and cathode includes cathode core components and the anode active material layer that is coated on the core components.The restriction site that there is battery limitation electrode assembly to vertically move, and meet relational expression: 0.965≤B/A≤0.995 from the restriction site to the distance A of battery case bottom interior surface and the width B of cathode.
The inner surface of battery case bottom has slight depressed section and protrusion.However, in the case, the difference in height between depressed section and protrusion is typically not greater than 0.05mm, therefore negligible.In addition, the width B of cathode refers to the length of the shorter edge of bar shaped cathode.That is, the width B of cathode corresponds in cylindrical electrode component at the maximum height of electrode section.
Lithium secondary battery according to the present invention has the diaphragm comprising the microporous barrier between porous heat-resistant layer and anode or between porous heat-resistant layer and cathode.
Porous heat-resistant layer is formed in, for example, on the surface of at least one in anode active material layer and anode active material layer.
Porous heat-resistant layer includes, for example, insulating packing and adhesive.On the basis of the insulating packing of 100 parts by weight, the content of adhesive is preferably 1~10 parts by weight.Porous heat-resistant layer preferably has 40~80% porosity.
Insulating packing preferably comprises inorganic oxide.Inorganic oxide preferably comprises at least one of aluminium oxide, silica, magnesia, titanium dioxide and zirconium oxide.
When electrode assembly is substantially cylindrical and battery case is cylindrical, the step for the battery case that restriction site is preferably reduced using the internal diameter that the battery shell side wall upper half is arranged in.When the change in depth for the step that distance A reduces according to diameter, the distance of the inner surface from the deepest part (protruding the best part towards the center of battery case) of step to battery case bottom is distance A.
Lithium secondary battery according to the present invention has the insulator between electrode assembly and sealing plate.In the case, when it is prismatic that electrode assembly, which is substantially elliptical cylindrical and battery case, restriction site is preferably the lower half surface of insulator.In prismatic lithium secondary battery, relational expression: 0.975≤B/A≤0.995 is preferably satisfied from restriction site to the distance A of the inner surface of battery case bottom and the width B of cathode.
Invention effect
The present invention can provide it is a kind of with outstanding resistance to shorting and heat resistance, be avoided that because impact is as capacitance loss and provided the lithium secondary battery of higher capacity caused by falling.
Detailed description of the invention
Fig. 1 is an exemplary diagrammatic cross-section of cylindrical lithium secondary battery of the invention；And
Fig. 2 is an exemplary diagrammatic cross-section of square lithium secondary battery of the invention.
Specific embodiment
The present invention relates to a kind of lithium secondary batteries comprising: there is bottom, side wall and open-topped battery case；Electrode assembly；Nonaqueous electrolytic solution；And open-topped sealing plate of the covering to the battery case of accommodate electrod component and electrolyte.The electrode assembly includes the bar shaped anode and bar shaped cathode being intertwined with the porous heat-resistant layer of insertion between a positive electrode and a negative electrode.Anode includes positive core components and the anode active material layer that is coated on the core components, and cathode includes cathode core components and the anode active material layer that is coated on the core components.The restriction site that there is battery limitation electrode assembly to vertically move, and meet relational expression: 0.965≤B/A≤0.995 from restriction site to the distance A of the inner surface of battery case bottom and the width B of cathode.
The present inventor has studied the electrode assembly with porous heat-resistant layer by persistence and has following two discoveries.
Firstly, the electrode assembly with porous heat-resistant layer has lesser deformation compared with the conventional electrode assemblies of not porous heat-resistant layer in charge/discharge process.This may be because porous heat-resistant layer has surface smoothness more lower than positive, cathode and diaphragm, and as a result electrode and diaphragm will not be slided or be moved.
Second, when there is no when appropriate deformation, which cannot be firmly secured in battery case for electrode assembly.Therefore, when this battery falls, the electrode in electrode assembly can be moved, so as to cause capacitance loss.
Based on these discoveries, in the present invention, the width B of cathode and the ratio (ratio of B/A) from restriction site to the distance A of the inner surface of battery case bottom are set as range more higher than conventional value.When the ratio of B/A meets relational expression: when 0.965≤B/A≤0.995, the movement (especially when battery falls) of electrode is obviously suppressed in electrode assembly, so that capacitance loss will not occur.
If the ratio of B/A is more than 0.96, the distortion of electrode assembly becomes larger, this normally results in short circuit.In addition, the cathode width of lithium secondary battery is usually designed to the width greater than anode, therefore the deformation of a cathode especially problem.However, even if the edge of cathode is slightly about deformed close to electrode assembly upper surface or lower surface, short circuit will not occur since the electrode assembly in the present invention has porous heat-resistant layer.Therefore, the ratio of B/A may be set to 0.965 or higher.According to the present invention, by making the width of cathode close to the distance A from restriction site to the inner surface of battery case bottom, high capacity can be realized while improving resistance to falling impacts.
If the ratio of B/A is difficult to realize high capacity less than 0.965, in addition, battery is likely to have capacitance loss because of the electrode movement in electrode assembly when falling.On the other hand, if the ratio of B/A is more than 0.995, cathode is having obvious deformation at electrode assembly upper surface or lower surface.Then, porous heat-resistant layer is destroyed, so that internal short-circuit be made to be prone to.
It is available that internal short-circuit, the lithium secondary battery with high capacity and outstanding resistance to falling impacts will not occur as 0.965≤B/A≤0.995.
Lithium secondary battery according to the present invention can have or without the diaphragm comprising microporous barrier.Diaphragm is between porous heat-resistant layer and anode or between porous heat-resistant layer and cathode.The effect of diaphragm is porous heat-resistant layer frangible in support construction.Therefore, to further increase resistance to falling impacts, battery preferably has diaphragm.
Microporous membrane material is preferably polyolefin, and the polyolefin is preferably polyethylene, polypropylene etc..It can also be used while comprising polyethylene and polyacrylic microporous barrier.Preferably 8~20 μm of the thickness of microporous barrier plays the role of supporting porous heat-resistant layer to ensure it and high capacity is kept to design.
Porous heat-resistant layer can be made only on the surface of anode active material layer or on the surface of anode active material layer.Alternatively, porous heat-resistant layer can be formed simultaneously on the surface of anode active material layer and the surface of anode active material layer.However, porous heat-resistant layer is preferably formed on the surface for being designed to there is greater area of anode active material layer than anode active material layer in order to avoid internal short-circuit with reliable fashion.In addition, on the active material layer that the porous heat-resistant layer can be formed on a side of core components or on the active material layer that is formed on two sides of core components.In addition, porous heat-resistant layer is preferably adhered on the surface of active material layer.
Porous heat-resistant layer can be independent thin slice.However, the mechanical strength not high due to lamelliform porous heat-resistant layer, therefore be likely difficult to handle.In addition, porous heat-resistant layer can be adhered on the surface of diaphragm.However, since diaphragm can be shunk at high temperature, therefore the manufacturing condition of porous heat-resistant layer must be kept a close eye on.Such issues that eliminate, porous heat-resistant layer also preferably form on the surface of anode active material layer or on the surface of anode active material layer.
Porous heat-resistant layer preferably comprises insulating packing and adhesive.Using scraping blade or die coater, the raw material slurry containing insulating packing and a small amount of adhesive is coated on the surface of electrode active material layers or diaphragm and after drying, forms the porous heat-resistant layer.Using a such as double-arm kneader, insulating packing, adhesive and liquid components are mixed, raw material slurry is prepared.
In addition, porous heat-resistant layer can be the fibroplastic film by the resin of high-fire resistance.The resin of high-fire resistance is preferably aromatic polyamides, polyamidoimide etc..However, the porous heat-resistant layer comprising insulating packing and adhesive has structural strength more higher than the fibroplastic film of high-fire resistance resin because of the effect of adhesive, therefore it is preferred.
The thickness of porous heat-resistant layer is preferably 0.5~20 μm, and further preferably 1~10 μm.If the thickness of porous heat-resistant layer is lower than 0.5 μm, the effect of internal short-circuit is inhibited to reduce.In addition, if the thickness of porous heat-resistant layer is more than 20 μm, distance is excessive between anode and cathode, this will lead to the output characteristics decline of battery.
Insulating packing may include the resin bead of fiber or high-fire resistance, it is preferred that including inorganic oxide.Since inorganic oxide is hard, even if therefore they can be such that the distance between anode and cathode is remained in suitable range when charge/discharge causes electrode expansion.In inorganic oxide, particularly preferably such as aluminium oxide, silica, magnesia, titanium dioxide and zirconium oxide, this is because their electrochemical stabilities with higher in the working environment of lithium secondary battery.They can individually or two or more are applied in combination.
In the porous heat-resistant layer comprising insulating packing and adhesive, on the basis of the insulating packing of 100 parts by weight, the content of adhesive is preferably 1~10 parts by weight, and further preferably 2~8 parts by weight, to keep the mechanical strength and its ionic conductivity of porous heat-resistant layer.Most of adhesive and thickener can occur inherently to be swollen due to the electrolyte containing nonaqueous solvents.Therefore, if the content of adhesive is more than 10 parts by weight, adhesive, which can be excessively swollen, is closed the micropore of porous heat-resistant layer, to make ionic conductivity reduce and prevent cell reaction.On the other hand, if the content of adhesive is lower than 1 parts by weight, the mechanical strength of porous heat-resistant layer is reduced.
It is not particularly limited for the adhesive in porous heat-resistant layer, but preferably such as polyvinylidene fluoride (hereinafter referred to as PVDF), polytetrafluoroethylene (PTFE) (hereinafter referred to as PTFE) and polyacrylie-type rubber particles (such as BM-500B (trade name) of Zeon company).It is preferred that PTFE or BM-500B and thickening agent combination are used.Thickener is not particularly limited, but preferably such as carboxymethyl cellulose (hereinafter referred to as CMC), polyethylene oxide (hereinafter referred to as PEO) and modified butadiene acrylonitrile rubber (such as BM-720H (trade name) of Zeon company).
The porosity of porous heat-resistant layer comprising insulating packing and adhesive is preferably 40%~80%, and further preferably 45%~65%, to keep the mechanical strength of porous heat-resistant layer and improve its resistance to falling impacts.Since porous heat-resistant layer has surface smoothness more lower than positive, cathode and diaphragm, therefore the sliding (movement) of electrode and diaphragm is greatly suppressed.Then, electrode assembly is be easily moved.However, electrode assembly can swell to suitable degree when the porous heat-resistant layer with 40%~80% porosity immerses appropriate electrolyte.Then, the electrode assembly of swelling presses the inner sidewall of battery case.When the effect of effect and B/A optimum ratio that 40%~80% porosity generates promotes mutually, resistance to falling impacts are further enhanced.If porosity is lower than 40%, electrolyte does not have abundant impregnating porous refractory layer, and then electrode assembly does not swell to suitable degree.On the other hand, if porosity is more than 80%, the mechanical strength of porous heat-resistant layer is reduced.
It will be noted that the porosity of porous heat-resistant layer can be controlled by changing median particle diameter, the content of adhesive and the drying condition of raw material slurry of insulating packing.It can lead to porosity relative increase for example, increasing drying temperature or increasing desiccant hot air flowrate.Porosity can be calculated by following parameter, for example, the actual specific gravity of the thickness of porous heat-resistant layer, the content of insulating packing and adhesive and insulating packing and adhesive.The thickness of porous heat-resistant layer can be determined by the SEM photograph of several cross sections (such as 10 cross sections) of shooting electrode and the average thickness of these cross sections.In addition, porosity can be determined with mercury porosimeter.
The electrode assembly for the cylinder (cylinder) that cylindrical lithium secondary battery has section substantially circular.In addition, cylindrical lithium secondary battery has column-shaped battery case 100 as shown in Figure 1.The column-shaped battery case is open at one end and the other end is closed with flat 110.For common cylindrical lithium secondary battery, the opening edge of battery case is crimped on the circumference of sealing plate 120 to seal its top opening.In the case, the restriction site that limitation electrode assembly vertically moves is the step 130 with the battery case 100 for reducing internal diameter that the 100 side wall upper half of battery case is arranged in.Step 130 also has the function of fixing seal plate 120.
It is the electrode assembly of substantially elliptical cylindrical (cylinder of nearly ellipse) that prismatic lithium secondary battery, which has cross section,.In addition, square lithium secondary battery has prismatic (essentially rectangular) battery case 200 as shown in Figure 2.The prismatic battery shell is open at one end and the other end is closed with flat 210.For common square lithium secondary battery, the top opening of battery case is by welding together sealing for its opening edge and metal sealing plate 220.In addition, insulator 230 (upper portion insulating body) prevents lead and battery case 200 in electrode from contacting between sealing plate 220 and electrode assembly.Insulator 230 has contact conductor through-hole, so that insulator be made hardly to move.Therefore, the restriction site that limitation electrode assembly vertically moves is the lower surface of insulator 230.
The thickness of insulator is preferably the 2%~10% of battery case height, so that it is guaranteed that its function and reducing dead angle.
In cylindrical lithium secondary battery, the vertical section of the step as restriction site is limited by production method is generally V-arrangement or U-shaped.Therefore, depth of the variation of distance A dependent on the step as restriction site.In the case, the distance of the inner surface from step deepest part to battery case bottom is distance A.In the case, if the ratio of B/A is 0.965 or more, enough resistance to falling impacts can be obtained.However, it is contemplated that the balance of high capacity and resistance to falling impacts, more preferably 0.970≤B/A≤0.990 in cylindrical lithium secondary battery.
On the other hand, in square lithium secondary battery, the lower surface of the insulator 230 as restriction site is flat.Therefore, the resistance to falling impacts outstanding for acquisition, the ratio of B/A preferably 0.975 or more.In addition, it is contemplated that the balance of high capacity and resistance to falling impacts, more preferably 0.975≤B/A≤0990 in square lithium secondary battery.
Anode includes positive core components and the anode active material layer being coated on each side of the core components.Positive core components is the bar shapeds suitable for winding and contain Al, Al alloy etc..The optional components such as conductive agent and adhesive that anode active material layer may include comprising the positive electrode active materials as basic component and optionally.These materials are not particularly limited, it is preferable that positive electrode active materials are the transition metal oxide containing lithium.In the transition metal oxide containing lithium, preferably such as cobalt acid lithium, modified cobalt acid lithium, lithium nickelate, modified lithium nickelate, LiMn2O4 and modified lithium manganate.
Cathode includes cathode core components and the anode active material layer that is coated on each side of the core components.Cathode core components is the bar shapeds suitable for winding and contain Cu, Cu alloy etc..The width B of cathode is equal to the width of cathode core components.The optional components such as conductive agent and adhesive that anode active material layer may include comprising the negative electrode active material as basic component and optionally.These materials are not particularly limited, but preferred negative electrode active material includes various natural graphites, various artificial graphites, siliceous composite material such as silicide, lithium metal and various alloy materials.
The adhesive for positive or negative pole enumerated includes PTFE, PVDF and butadiene-styrene rubber.The conductive agent enumerated includes acetylene black, Ketjen black (registered trademark) and various graphite.
Nonaqueous electrolytic solution preferably comprises nonaqueous solvents and is dissolved in lithium salts therein.Lithium salts is not particularly limited, but preferably such as LiPF6 and LiBF4.These lithium salts can be used alone, and can also be used with combination of two or more.Nonaqueous solvents is not particularly limited, but preferred example includes ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC).These nonaqueous solvents can be used alone, and can also be used with combination of two or more.
The material of battery case must be electrochemically stable in the operating voltage range of lithium secondary battery.For example, it is preferable to use iron or aluminium.In addition, battery case can be electroplated with nickel or tin.
Fig. 1 is the diagrammatic cross-section of the cylindrical lithium secondary battery of the invention of demonstration.
By the way that anode 101 and cathode 102 are intertwined with the porous heat-resistant layer (not shown) of diaphragm 103 and insertion between a positive electrode and a negative electrode, cylindrical electrode component is produced.Diaphragm 103 is located between porous heat-resistant layer and anode 101.However, diaphragm 103 is unwanted if porous heat-resistant layer has enough thickness.Electrode assembly is inserted into column-shaped battery case 100.The step 130 that there is an internal diameter to be relatively shorter than other parts for the upper half of 100 side wall of battery case.Step 130 is formed after electrode assembly is put into battery case 100.The vertical section of step 130 is U-shaped.Later, it injects the electrolyte into battery case 100.The top opening of battery case 100 is sealed by installing sealing plate 120 on step 130 and the opening edge of battery case 100 being crimped on the circumference of sealing plate 120.
The top of electrode assembly and beneath is arranged in the negligible upper portion insulating body plate 106 of thickness and lower isolator plate 107.One end of positive wire 104 is connected to the core components of anode 101, and the other end is connected to the inside end 108a being arranged on 120 lower surface of sealing plate.It is continuous between internal end 108a and external positive end 108.One end of cathode conductor (not shown) is connected to the core components of cathode 102, and the other end is connected to the inner bottom surface of battery case 100.
Fig. 2 is the diagrammatic cross-section of the square lithium secondary battery of the invention of demonstration.
By the way that anode and cathode are intertwined with the porous heat-resistant layer of diaphragm and insertion between a positive electrode and a negative electrode, the cylindrical electrode component of nearly ellipse is produced.Electrode assembly 201 is inserted into essentially rectangular (prismatic) battery case 200.After electrode assembly 201 is put into battery case 200, insulator 230 is mounted on the top of electrode assembly 201 to prevent the short circuit between one end of battery case 200 or positive wire 202 and cathode conductor 203.Insulator 230 is fixed near the opening of battery case 200.
The negative end 207 that there is sealing plate 220 periphery to be furnished with insulation spacer 206.Cathode conductor 203 is connected to negative end 207, and positive wire 202 is connected to the lower surface of sealing plate 220.
Electrolyte is injected into battery case 200 from the injection hole in sealing plate 220, and the injection hole is sealed by welding sealing-plug 209.The top opening of battery case 200 is sealed by assembly sealing plate 220 and with laser welding opening edge and sealing plate 220.
Citing is illustrated into the contents of the present invention below.
Embodiment 1
In this embodiment, explanation is cylindrical lithium secondary battery shown in FIG. 1.
(battery 1)
(i) positive preparation
Use a double arm kneading mixer, PVDF#1320 (n-methyl-2-pyrrolidone (hereinafter referred to as NMP) solution containing 12wt%PVDF), the acetylene black of 90g and the suitable NMP of the cobalt acid lithium of 3kg, the Kureha chemical industry Co., Ltd of 1kg are stirred, cathode mix slurry is prepared.Resulting slurry is coated on two sides of the positive core components comprising 15 μ m-thick aluminium foils, forms the anode with anode active material layer after dry and roll-in.The overall thickness of the anode is 160 μm.The anode is cut into the band that width is 56.5mm.
(ii) preparation of cathode
Using a double-arm kneader, BM-400B (aqueous dispersion of the modified styrene butadiene rubber containing 40wt%), the CMC of 30g and the suitable water of the Zeon company of the artificial graphite of 3kg, 75g are stirred, negative electrode mix slurry is prepared.Resulting slurry is coated on two sides of the cathode core components comprising 10 μ m-thick copper foils, forms the cathode with anode active material layer after dry and roll-in.The overall thickness of the cathode is 180 μm.The cathode is cut into the band that width is 57.5mm.
(iii) formation of porous heat-resistant layer
Use a double-arm kneader, BM-720H (nmp solution (adhesive) of the nitrile rubber of modified polypropene containing 8wt%) and suitable NMP by the median particle diameter of 970g for 0.3 μm of aluminium oxide (insulating packing), the Zeon company of 375g are stirred, and prepare raw material slurry.Resulting raw material slurry is coated on the surface of anode active material layer, and 4 minutes dry with 130 DEG C of hot-air (flow: 1.5m/min), to form the porous heat-resistant layer of 5 μ m-thicks.The porosity of each porous heat-resistant layer is 50%.Porosity is calculated according to following parameter: the thickness for the porous heat-resistant layer that the SEM photograph by shooting its cross section determines；The content of aluminium oxide in the porous heat-resistant layer of the given area obtained by x-ray fluorescence analysis；The actual specific gravity of aluminium oxide and adhesive；And the weight ratio between aluminium oxide and adhesive.
(iv) preparation of electrolyte
LiPF6 is dissolved in the solvent mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) that volume ratio is 1: 1: 1 with the concentration of 1mol/liter, and the ethylene carbonate of the solution and 3wt% are mixed, electrolyte is prepared.
(v) manufacture of battery
By the way that the diaphragm of the cathode and anode and the polyethene microporous membrane (purchased from Celgard K.K., width: 60.7mm) for 10 μ m-thicks being interposed therebetween that form porous heat-resistant layer on two sides is intertwined, cylindrical electrode component is produced.
Then the electrode assembly is inserted into in the column-shaped battery case of the iron of nickel plating (internal diameter: 18mm).It should be noted that upper portion insulating body plate and lower isolator plate are located at the top of electrode assembly and beneath, because they are very thin, therefore its thickness is negligible.Thereafter, one step is set in the upper half of battery shell side wall, the internal diameter of battery case is to reduce herein.The vertical section of the step is U-shaped, and the depth of the step of diameter reduction is 1.5 μm.The distance A of deepest part from the inner bottom surface of battery case to the step is 60.5mm.
The electrolyte of 5.5g is then injected into the hollow portion of electrode assembly, so that electrode assembly be made to immerse electrolyte.Thereafter, sealing plate is mounted on the step of battery case, and the opening edge of battery case is crimped on the circumference of sealing plate.The internal diameter of the cylindrical lithium secondary battery produced is 18mm, is highly 65.0mm, and design capacity is 2200mAh.The ratio (the width B (57.5mm) of cathode and the ratio of distance A (60.5mm)) of B/A is 0.950.
(battery 2~5)
Cylindrical lithium secondary battery 2~5 is made with manufacturing method identical with battery 1, different only cathode width B become 58.5mm, 59.2mm, 60.2mm and 61.2mm respectively, positive width becomes 57.5mm, 58.2mm, 59.2mm and 60.2mm respectively, and design capacity becomes 2239mAh, 2266mAh, 2305mAh and 2244mAh respectively.The ratio of B/A is 0.967 (battery 2), 0.979 (battery 3), 0.995 (battery 4) and 1.012 (batteries 5) in various batteries.
(battery 6)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 3, different only porous heat-resistant layers is formed on the surface of anode active material layer without on the surface of anode active material layer.
(battery 7)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 4, different only porous heat-resistant layers is formed on the surface of anode active material layer without on the surface of anode active material layer.
(battery 8)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 3, the thickness of different only porous heat-resistant layers becomes 15 μm and do not manufacture electrode assembly with diaphragm.
(battery 9)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 3, the aluminium oxide in different only porous heat-resistant layers becomes the magnesia with same median partial size.
(battery 10)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 3, the aluminium oxide in different only porous heat-resistant layers becomes the silica with same median partial size.
(battery 11)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 3, the aluminium oxide in different only porous heat-resistant layers becomes the titanium dioxide with same median partial size.
(battery 12)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 3, the aluminium oxide in different only porous heat-resistant layers becomes the zirconium oxide with same median partial size.
(battery 13)
The forming process of porous heat-resistant layer is as follows.
The dry anhydrous calcium chloride of 65g is added in the NMP of 1kg, and heats the mixture to 80 DEG C in the reactor and makes it completely dissolved.The nmp solution of resulting calcium chloride is cooled to room temperature, then the p-phenylenediamine of 32g is added thereto and is completely dissolved.Thereafter, reactor is placed in 20 DEG C of thermostatic chamber, and gradually the dichloroterephthalicacid acid of 58g is added in nmp solution in 1 hour.The nmp solution is placed 1 hour in 20 DEG C of thermostatic chambers so that polymerization reaction carries out, to synthesize poly(p-phenylene terephthalamide) (hereinafter referred to as PPTA).
After completion of the reaction, nmp solution (polymer fluid) is relayed from thermostatic chamber to vacuum chamber and depressurizes stirring 30 minutes with degasification.Resulting polymer fluid is diluted with the nmp solution of calcium chloride, prepares the nmp solution of the aromatic polyamide resin containing 1.4wt%PPTA.
The nmp solution of resulting aromatic polyamide resin is applied on surface on one surface of the membrane with scraping blade and is dried with 80 DEG C of hot-air (flow: 0.5m/sec).Resulting aromatic polyamide resin film is cleaned, sufficiently with pure water to remove calcium chloride and form micro- stomata in the film.Then by the film drying, to form the porous heat-resistant layer of 5 μ m-thicks on one surface of the membrane.The porosity of the porous heat-resistant layer is 48%.Electrode assembly manufacture is at making porous heat-resistant layer be in contact with anode.Porous heat-resistant layer is not formed in anode active material layer.In addition to above-mentioned difference, cylindrical lithium secondary battery is made with manufacturing method identical with battery 3.
(battery 14)
The forming process of porous heat-resistant layer is as follows.
The diaminodiphenyl ether of three acid anhydrides of monochloro-benzene of 21g and 20g is added in the NMP of 1kg, and they are mixed at room temperature, prepares the nmp solution (polyamide acid content: 3.9wt%) of polyamic acid.Resulting polyamic acid nmp solution is applied on surface on one surface of the membrane with scraping blade.By resulting coated film with 80 DEG C of hot-air dry (flow: 0.5m/sec) so that polyamic acid is dehydrated cyclization, to form polyamidoimide.By this method, the porous heat-resistant layer of 5 μ m-thicks is formed on one surface of the membrane.The porosity of the porous heat-resistant layer is 47%.Component manufacture in pole is at making porous heat-resistant layer be in contact with anode.Porous heat-resistant layer is not formed in anode active material layer.In addition to these differences, cylindrical lithium secondary battery is made with manufacturing method identical with battery 3.
(battery 15)
The nmp solution of the aromatic polyamide resin made from method identical with battery 13 is coated on smooth stainless steel (SUS) plate with scraping blade, and by resulting film 120 DEG C, be dried under reduced pressure 10 hours.Then the film is separated from SUS plate, to obtain the porous heat-resistant layer of the individual sheets formula of 15 μ m-thicks.The porosity of the porous heat-resistant layer is 51%.By by anode and cathode and the porous heat-resistant layer of the sheet type being interposed therebetween, but do not include diaphragm, is intertwined, produces electrode assembly.Porous heat-resistant layer is not formed in anode active material layer.In addition to above-mentioned difference, cylindrical lithium secondary battery is made with manufacturing method identical with battery 3.
(battery 16)
The nmp solution of the polyamic acid made from method identical with battery 14 is coated on smooth stainless steel (SUS) plate with scraping blade.Resulting coating is dry so that polyamic acid is dehydrated cyclization with 80 DEG C of hot-air (flow: 0.5m/sec).Then film is separated from SUS plate, to obtain the porous heat-resistant layer of the individual sheets formula of 15 μ m-thicks.The porosity of the porous heat-resistant layer is 52%.By by anode and cathode and the porous heat-resistant layer of the sheet type being interposed therebetween, but do not include diaphragm, is intertwined, produces electrode assembly.Porous heat-resistant layer is not formed in anode active material layer.In addition to above-mentioned difference, cylindrical lithium secondary battery is made with manufacturing method identical with battery 3.
(battery 17)
The forming process of porous heat-resistant layer is as follows.
Using a double-arm kneader, the BM-720H and suitable NMP of the aluminium oxide (median particle diameter is 0.3 μm) of 995g, the Zeon company of 62.5g are stirred, raw material slurry is prepared.Resulting raw material slurry is coated on the surface of anode active material layer, and 4 minutes dry with 130 DEG C of hot-air (flow: 1.5m/min), to form the porous heat-resistant layer of 5 μ m-thicks.The porosity of each porous heat-resistant layer is 61%.In addition to these differences, cylindrical lithium secondary battery is made with manufacturing method identical with battery 3.
(battery 18)
The forming process of porous heat-resistant layer is as follows.
Using a double-arm kneader, the BM-720H and suitable NMP of the aluminium oxide (median particle diameter is 0.3 μm) of 990g, the Zeon company of 125g are stirred, raw material slurry is prepared.Resulting raw material slurry is coated on the surface of anode active material layer, and 4 minutes dry with 130 DEG C of hot-air (flow: 1.5m/min), to form the porous heat-resistant layer of 5 μ m-thicks.The porosity of each porous heat-resistant layer is 57%.In addition to these differences, cylindrical lithium secondary battery is made with manufacturing method identical with battery 3.
(battery 19)
The forming process of porous heat-resistant layer is as follows.Using a double-arm kneader, the BM-720H and suitable NMP of the aluminium oxide (median particle diameter is 0.3 μm) of 900g, the Zeon company of 1250g are stirred, raw material slurry is prepared.Resulting raw material slurry is coated on the surface of anode active material layer, and 4 minutes dry with 130 DEG C of hot-air (flow: 1.5m/mim), to form the porous heat-resistant layer of 5 μ m-thicks.The porosity of each porous heat-resistant layer is 42%.In addition to these differences, cylindrical lithium secondary battery is made with manufacturing method identical with battery 3.
(battery 20)
The forming process of porous heat-resistant layer is as follows.
Using a double-arm kneader, the BM-720H and suitable NMP of the aluminium oxide (median particle diameter is 0.3 μm) of 800g, the Zeon company of 2500g are stirred, raw material slurry is prepared.Resulting raw material slurry is coated on the surface of anode active material layer, and 4 minutes dry with 130 DEG C of hot-air (flow: 1.5m/mim), to form the porous heat-resistant layer of 5 μ m-thicks.The porosity of each porous heat-resistant layer is 35%.In addition to these differences, cylindrical lithium secondary battery is made with manufacturing method identical with battery 3.
(battery 21~25)
Cylindrical lithium secondary battery 21~25 is made with manufacturing method identical with battery 3, the different raw material slurries for being only intended to dry coating becomes 0.5m/min, 1m/min, 2m/min, 5m/min and 8m/min with the flow for forming the hot-air of porous heat-resistant layer process respectively.The porosity of the porous heat-resistant layer of various batteries is 30% (battery 21), 42% (battery 22), 60% (battery 23), 78% (battery 24) and 89% (battery 25).
(battery 26)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 1, the thickness of different only diaphragms becomes 15 μm and formed without porous heat-resistant layer.
(battery 27)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 2, the thickness of different only diaphragms becomes 15 μm and formed without porous heat-resistant layer.
(battery 28)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 3, the thickness of different only diaphragms becomes 15 μm and formed without porous heat-resistant layer.
(battery 29)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 4, the thickness of different only diaphragms becomes 15 μm and formed without porous heat-resistant layer.
(battery 30)
Cylindrical lithium secondary battery is made with manufacturing method identical with battery 5, the thickness of different only diaphragms becomes 15 μm and formed without porous heat-resistant layer.
Various batteries are pre-charged and are discharged twice, and preservation 7 days under 45 DEG C of environment.Later, they are assessed as follows.Table 1, table 2 and table 3 summarise the feature, battery design and assessment result of porous heat-resistant layer respectively.
(internal short-circuit inspection)
Various batteries manufacture 100 samples.Electric discharge is carried out as follows in the environment of 20 DEG C in these Sample Cells, and measures their open-circuit voltage.Thereafter, these batteries preservation 10 days and are measured into their open-circuit voltage under 45 DEG C of environment again.When open-circuit voltage difference of the battery under 45 DEG C of environment before and after preservation is 0.3V or more, it may be determined that this kind of battery is in internal short-circuit state.The incidence of internal short-circuit is as shown in table 3.
Constant-current charge: charging current 1500mA/ end of charge voltage 4.2V；
Constant-voltage charge: charging voltage 4.2V/ charging termination electric current 100mA.
(drop test)
Charging and discharging are carried out as follows in battery by internal short-circuit inspection under 20 DEG C of environment, and obtain their discharge capacity.
Constant-current charge: charging current 1500mA/ end of charge voltage 4.2V；
Constant-voltage charge: charging voltage 4.2V/ charging termination electric current 100mA；
Constant-current discharge: discharge current 2200mA/ final discharging voltage 3V.
Thereafter, these batteries repeat to fall 30 times under 20 DEG C of environment from 16cm eminence, then charge and discharge by above-mentioned condition, and obtain their discharge capacity.Then percentage of the discharge capacity with respect to discharge capacity before drop test after acquisition drop test.The results are shown in Table 3 for resistance to falling impacts.
(internal short-circuit inspection after drop test)
After drop test, internal short-circuit of battery is checked with method identical before drop test.The results are shown in Table 3 for lower backward internal short-circuit incidence.
(high output characteristic)
Charging and discharging are carried out as follows in various batteries under 20 DEG C of environment, and obtain their discharge capacity.
Constant-current charge: charging current 1500mA/ end of charge voltage 4.2V；
Constant-voltage charge: charging voltage 4.2V/ charging termination electric current 100mA；
Constant-current discharge: discharge current 440mA/ final discharging voltage 3V；
Constant-current charge: charging current 1500mA/ end of charge voltage 4.2V；
Constant-voltage charge: charging voltage 4.2V/ charging termination electric current 100mA；
Constant-current discharge: discharge current 4400mA/ final discharging voltage 3V.
Then it can get battery in percentage of the discharge capacity under 4400mA with respect to its discharge capacity at 440mA.The results are shown in Table 3 for high output characteristic.
(nail puncture test)
Various batteries charge to the blanking voltage of 4.35V under the charging current of 2200mA.In the environment of 20 DEG C, iron nail (diameter 2.7mm) is knocked in the side wall of the battery of various chargings with the speed of 5mm/sec, and measures battery temperature with the thermocouple invested on battery side wall.Battery temperature after 90 seconds is as shown in table 3.
Table 1
| Battery | Porous heat-resistant layer (μm) | The position of porous heat-resistant layer | Diaphragm (μm) | Filler | Binder content (wt%) | Porosity (%) |
| 1 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 2 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 3 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 4 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 5 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 6 | 5 | Anode | 10 | Aluminium oxide | 3 | 50 |
| 7 | 5 | Anode | 10 | Aluminium oxide | 3 | 50 |
| 8 | 15 | Cathode | Nothing | Aluminium oxide | 3 | 50 |
| 9 | 5 | Cathode | 10 | Magnesia | 3 | 50 |
| 10 | 5 | Cathode | 10 | Silica | 3 | 50 |
| 11 | 5 | Cathode | 10 | Titanium dioxide | 3 | 50 |
| 12 | 5 | Cathode | 10 | Zirconium oxide | 3 | 50 |
| 13 | 5 | Diaphragm | 10 | Aromatic polyamides | - | 48 |
| 14 | 5 | Diaphragm | 10 | Polyamidoimide | - | 47 |
| 15 | 15 | Independent thin slice | Nothing | Aromatic polyamides | - | 51 |
| 16 | 15 | Independent thin slice | Nothing | Polyamidoimide | - | 52 |
| 17 | 5 | Cathode | 10 | Aluminium oxide | 0.5 | 61 |
| 18 | 5 | Cathode | 10 | Aluminium oxide | 1 | 57 |
| 19 | 5 | Cathode | 10 | Aluminium oxide | 10 | 42 |
| 20 | 5 | Cathode | 10 | Aluminium oxide | 20 | 35 |
| 21 | 5 | Cathode | 10 | Aluminium oxide | 3 | 30 |
| 22 | 5 | Cathode | 10 | Aluminium oxide | 3 | 42 |
| 23 | 5 | Cathode | 10 | Aluminium oxide | 3 | 60 |
| 24 | 5 | Cathode | 10 | Aluminium oxide | 3 | 78 |
| 25 | 5 | Cathode | 10 | Aluminium oxide | 3 | 89 |
| 26 | Nothing | - | 15 | - | - | - |
| 27 | Nothing | - | 15 | - | - | - |
| 28 | Nothing | - | 15 | - | - | - |
| 29 | Nothing | - | 15 | - | - | - |
| 30 | Nothing | - | 15 | - | - | - |
Table 2
| Battery | Cathode width B (mm) | Positive width (mm) | Design capacity (mAh) | B/A |
| 1 | 57.5 | 56.5 | 2200 | 0.950 |
| 2 | 58.5 | 57.5 | 2239 | 0.967 |
| 3 | 59.2 | 58.2 | 2266 | 0.979 |
| 4 | 60.2 | 59.2 | 2305 | 0.995 |
| 5 | 61.2 | 60.2 | 2344 | 1.012 |
| 6 | 59.2 | 58.2 | 2266 | 0.979 |
| 7 | 60.2 | 59.2 | 2305 | 0.995 |
| 8 | 59.2 | 58.2 | 2266 | 0.979 |
| 9 | 59.2 | 58.2 | 2266 | 0.979 |
| 10 | 59.2 | 58.2 | 2266 | 0.979 |
| 11 | 59.2 | 58.2 | 2266 | 0.979 |
| 12 | 59.2 | 58.2 | 2266 | 0.979 |
| 13 | 59.2 | 58.2 | 2266 | 0.979 |
| 14 | 59.2 | 58.2 | 2266 | 0.979 |
| 15 | 59.2 | 58.2 | 2266 | 0.979 |
| 16 | 59.2 | 58.2 | 2266 | 0.979 |
| 17 | 59.2 | 58.2 | 2266 | 0.979 |
| 18 | 59.2 | 58.2 | 2266 | 0.979 |
| 19 | 59.2 | 58.2 | 2266 | 0.979 |
| 20 | 59.2 | 58.2 | 2266 | 0.979 |
| 21 | 59.2 | 58.2 | 2266 | 0.979 |
| 22 | 59.2 | 58.2 | 2266 | 0.979 |
| 23 | 59.2 | 58.2 | 2266 | 0.979 |
| 24 | 59.2 | 58.2 | 2266 | 0.979 |
| 25 | 59.2 | 58.2 | 2266 | 0.979 |
| 26 | 57.5 | 56.5 | 2200 | 0.950 |
| 27 | 58.5 | 57.5 | 2239 | 0.967 |
| 28 | 59.2 | 58.2 | 2266 | 0.979 |
| 29 | 60.2 | 59.2 | 2305 | 0.995 |
| 30 | 61.2 | 60.2 | 2344 | 1.012 |
Table 3
| Battery | Short-circuit incidence (%) | Resistance to falling impacts (%) | Lower backward short-circuit incidence (%) | High output characteristic (%) | Battery temperature (DEG C) after sting |
| 1 | 0 | 93.0 | 2 | 90.3 | 86 |
| 2 | 0 | 99.8 | 1 | 91.4 | 85 |
| 3 | 0 | 99.9 | 0 | 90.6 | 84 |
| 4 | 0 | 99.7 | 0 | 92.3 | 86 |
| 5 | 24 | 99.8 | 2 | 91.9 | 83 |
| 6 | 2 | 100.0 | 0 | 90.2 | 83 |
| 7 | 14 | 99.5 | 9 | 88.7 | 90 |
| 8 | 3 | 99.7 | 19 | 86.6 | 83 |
| 9 | 0 | 99.7 | 0 | 88.9 | 84 |
| 10 | 0 | 99.8 | 0 | 88.7 | 86 |
| 11 | 0 | 99.9 | 2 | 88.6 | 81 |
| 12 | 0 | 99.9 | 0 | 88.9 | 86 |
| 13 | 0 | 99.7 | 8 | 89.2 | 86 |
| 14 | 0 | 99.6 | 9 | 89.5 | 82 |
| 15 | 3 | 99.5 | 16 | 90.1. | 91 |
| 16 | 1 | 99.8 | 14 | 90.6 | 92 |
| 17 | 0 | 99.8 | 11 | 90.1 | 94 |
| 18 | 0 | 99.8 | 0 | 88.9 | 89 |
| 19 | 0 | 99.8 | 2 | 83.8 | 80 |
| 20 | 0 | 99.9 | 0 | 79.5 | 80 |
| 21 | 0 | 95.7 | 0 | 82.4 | 83 |
| 22 | 0 | 98.6 | 0 | 87.9 | 84 |
| 23 | 0 | 99.8 | 0 | 89.0 | 88 |
| 24 | 0 | 99.7 | 6 | 90.5 | 85 |
| 25 | 0 | 100.0 | 10 | 93.4 | 90 |
| 26 | 0 | 99.7 | 0 | 88.1 | 128 |
| 27 | 15 | 99.9 | 0 | 88.2 | 124 |
| 28 | 22 | 99.8 | 0 | 87.9 | 126 |
| 29 | 30 | 99.8 | 0 | 89.1 | 130 |
| 30 | 46 | 99.8 | 0 | 88.8 | 124 |
Opposite from step (restriction site) battery 1 too small to the distance A of battery case inner bottom surface in cathode width B, capacity density is smaller, and furthermore resistance to falling impacts are lower.After drop test, battery 1 is dismantled and is observed, as a result, it has been found that the electrode of winding electrode assembly has movement.
Because of the effect of porous heat-resistant layer internal short-circuit does not occur for battery 1, but the reduction of effective area (anode and cathode area relative to each other) leads to its capacitance loss.Because being furnished with porous heat-resistant layer, electrode assembly can resist deformation, therefore its inside that cannot be firmly secured to battery case.Therefore the electrode for winding electrode assembly may be moved when repeating to fall.
On the other hand, opposite from the step battery 5 excessive to the distance A of battery case inner bottom surface in cathode width B, resistance to short-circuit is lower.The sample for determining the battery 5 in internal short-circuit state is dismantled and is observed.As a result, it has been found that the porous heat-resistant layer in negative terminal surface has damage in the upper half of electrode assembly.It has also been found that diaphragm cracks.
B/A ratio in 0.965~0.995 battery 2~4, resistance to short-circuit is higher, and furthermore resistance to falling impacts are improved.Battery of the invention is also equipped with porous heat-resistant layer in addition to diaphragm.Therefore, even if making deformed part insulate by the double-layer structure that porous heat-resistant layer and diaphragm form when cathode is wider than anode, there is slight deformation in the electrode assembly upper half.Further, since the ratio of B/A is higher, electrode assembly is firmly sandwiched between step and the inner bottom surface of battery case.Therefore the resistance to falling impacts of battery may be improved.
In the battery 26~30 of not porous heat-resistant layer, the influence of the resistance to unrestricted site location of falling impacts is excellent.It is believed that the electrode assembly of porous heat-resistant layer is not deformed to an appropriate level, therefore it is firmly secured in battery case.Even if causing the electrode movement of the winding electrode assembly of capacitance loss that may therefore be suppressed when these batteries fall.However, these batteries 26~30 obviously overheat in nail puncture test.In addition, resistance to short-circuit is lower in restriction site position respectively battery 27~29 identical with battery 2~4.It is believed that the cathode of these batteries 27~29 has slight deformation.However, when diaphragm cracks because of cathode deformation, internal short-circuit cannot prevent since these batteries do not have porous heat-resistant layer.
In battery 6 and 7, porous heat-resistant layer is formed on the surface of anode active material layer.In both batteries, the battery 7 with wider cathode shows relatively low resistance to short-circuit.This may be because porous heat-resistant layer is formed on the surface of the anode active material layer more narrower than anode active material layer, and then negative terminal surface is in contact in the upper half of electrode assembly with the top edge of anode.
In not having septate battery 8, the resistance to short-circuit after falling is slightly lower.It is more more fragile than diaphragm in its porous heat-resistant layer structure.Then, porous heat-resistant layer is acted on and local damage by falling impacts, so that short circuit occur.
In the battery 13 and 14 that membrane surface has the porous heat-resistant layer made of heat stable resin, the resistance to short-circuit after falling is slightly lower.The mechanical strength of porous heat-resistant layer made of heat stable resin is lower than the mechanical strength of the porous heat-resistant layer comprising insulating packing and adhesive.Short circuit may therefore occur by falling impacts effect.
With independent porous heat-resistant layer thin slice and do not having in septate battery 15 and 16, their lower backward resistance to short-circuits are lower than battery 13 and the lower backward resistance to short-circuit of battery 14.This is derived from the fact, i.e. the intensity of porous heat-resistant layer intensity difference and porous heat-resistant layer made of heat stable resin is not improved because of lacking for diaphragm.
In porous heat-resistant layer in the battery 17 of the adhesive containing 0.5wt%, the resistance to short-circuit after falling is slightly lower.This may be the adhesion strength that filler grain is reduced because of the adhesive of low content, poor so as to cause the mechanical strength of porous heat-resistant layer.
On the other hand, in the battery 20 containing 20wt% adhesive, high output characteristic is lower.This may be because excessive adhesive reduces the porosity of porous heat-resistant layer, in addition, excessive adhesive is swollen with electrolyte, to make the micropore of porous heat-resistant layer be closed and reduce ionic conductivity.On the other hand, in the battery 18~19 that binder content is 1wt%~10wt%, resistance to short-circuit and high output characteristic are all excellent.
In the battery 21 of the porous heat-resistant layer with 30% porosity obtained by control drying condition, resistance to falling impacts are slightly lower.Its reason may be as follows.Since porosity is lower, porous heat-resistant layer is not sufficiently wet electrolyte, and then the swelling of electrode assembly is smaller.It is thus impossible to prevent electrode assembly mobile when falling.In the battery 25 of the porous heat-resistant layer with 89% porosity, the resistance to short-circuit after falling is slightly lower.This may be because the mechanical strength of porous heat-resistant layer is poor.
On the other hand, in the battery 22~24 for the porous heat-resistant layer for being 40%~80% with porosity, resistance to falling impacts are excellent with the resistance to short-circuit after falling.Its reason may be as follows.Due to optimized porosity, the mechanical strength of porous heat-resistant layer is maintained.In addition, porous heat-resistant layer swells to an appropriate level with electrolyte.As a result the movement of electrode assembly is prevented.
Embodiment 2
In this embodiment, explanation is square lithium secondary battery shown in Fig. 2.
(battery 31)
In addition to following difference, electrode assembly is made with manufacturing method same as Example 1.The overall thickness of anode becomes 150 μm, and positive width becomes 42.7mm.The overall thickness of cathode becomes 150 μm, and the width of cathode becomes 43.7mm.The width of diaphragm becomes 47mm.The shape of electrode assembly becomes elliptical cylinder.
Resulting electrode assembly is inserted into the prismatic battery shell of the aluminium of 49mm high (bottom thickness: 0.5mm), 34mm wide and 5.2mm thickness.After the insulator of 1.5mm thickness is mounted at the top of electrode assembly, 2.5g electrolyte same as Example 1 is injected into battery case.Distance A from the inner bottom surface of battery case to insulator lower surface is 46.0mm.It should be noted that the lower half of electrode assembly is insulated by heat insulating lamella and battery case, but since heat insulating lamella is very thin, thickness is negligible.
Thereafter, the rectangular seal plate of 1.0mm thickness is mounted on to the top opening of battery case, and with laser by the opening edge of battery case together with the peripheral solder of sealing plate.The height of manufactured square lithium secondary battery is 50mm, width 34mm, with a thickness of 5.2mm, design capacity 950mAh.The ratio (ratio of cathode width B (43.7mm) and distance A (46.0mm)) of B/A is 0.95.
(battery 32~35)
Square lithium secondary battery 32~35 is made with manufacturing method identical with battery 31, different only cathode width B become 44.6mm, 45mm, 45.7mm and 46.5mm respectively, positive width becomes 43.6mm, 44mm, 44.7mm and 45.5mm respectively, and design capacity becomes 970mAh, 979mAh, 994mAh and 1012mAh respectively.The ratio of B/A is 0.970 (battery 32), 0.978 (battery 33), 0.993 (battery 34) and 1.011 (batteries 35) in various batteries.
(battery 36 and 37)
Square lithium secondary battery 36 and 37 is made with manufacturing method identical with battery 33 and 34 respectively, different only porous heat-resistant layers is formed on the surface of anode active material layer without on the surface of anode active material layer.
(battery 38)
Square lithium secondary battery is made with manufacturing method identical with battery 33, the thickness of different only porous heat-resistant layers becomes 15 μm and do not manufacture electrode assembly with diaphragm.
(battery 39~42)
Square lithium secondary battery 39~42 is made with manufacturing method identical with battery 33, the aluminium oxide in different only porous heat-resistant layers becomes the magnesia with same median partial size, silica, titanium dioxide and zirconium oxide respectively.
(battery 43~50)
Square lithium secondary battery 43~50 is made with manufacturing method identical with battery 33, different has only used porous heat-resistant layer identical with battery 13~20 in embodiment 1 respectively.
(battery 51~55)
Square lithium secondary battery 51~55 is made with manufacturing method identical with battery 33, the different raw material slurries only to dry coating becomes 0.5m/min, 1m/min, 2m/min, 5m/min and 8m/min with the flow for forming the hot-air of porous heat-resistant layer respectively.The porosity of the porous heat-resistant layer of various batteries is 30% (battery 51), 42% (battery 52), 60% (battery 53), 78% (battery 54) or 89% (battery 55).
(battery 56~60)
Square lithium secondary battery 56~60 is made with manufacturing method identical with battery 31~35 respectively, the thickness of different only diaphragms becomes 15 μm and is not provided with porous heat-resistant layer.
Various batteries are pre-charged and are discharged twice, then preservation 7 days under 45 DEG C of environment.Later, they are assessed with such as under type.Table 4, table 5 and table 6 summarise the feature, battery design and assessment result of porous heat-resistant layer respectively.
(internal short-circuit inspection)
The internal short-circuit of these batteries is checked with method same as Example 1, different is that they charge by following condition.It the results are shown in Table 6.
Constant-current charge: charging current 665mA/ end of charge voltage 4.2V；
Constant-voltage charge: charging voltage 4.2V/ charging termination electric current 100mA.
(drop test)
The resistance to falling impacts of these batteries are evaluated with method same as Example 1, different is that charging and discharging are carried out as follows in they.It the results are shown in Table 6.
Constant-current charge: charging current 665mA/ end of charge voltage 4.2V；
Constant-voltage charge: charging voltage 4.2V/ charging termination electric current 100mA；
Constant-current discharge: discharge current 950mA/ final discharging voltage 3V.
After (internal short-circuit inspection after drop test) drop test, with the internal short-circuit for checking these batteries with method identical before drop test.Short-circuit incidence after falling the results are shown in Table 6.
(high output characteristic)
Under 20 DEG C of environment, electric discharge and charging is carried out as follows in various batteries, and obtains their discharge capacity.
Constant-current charge: charging current 665mA/ end of charge voltage 4.2V；
Constant-voltage charge: charging voltage 4.2V/ charging termination electric current 100mA；
Constant-current discharge: discharge current 190mA/ final discharging voltage 3V；
Constant-current charge: charging current 665mA/ end of charge voltage 4.2V；
Constant-voltage charge: charging voltage 4.2V/ charging termination electric current 100mA；
Constant-current discharge: discharge current 1900mA/ final discharging voltage 3V.
Then it can get battery in percentage of the discharge capacity under 1900mA with respect to its discharge capacity at 190mA.High output characteristic the results are shown in Table 6.
(nail puncture test)
Various batteries charge to the blanking voltage of 4.35V under the charging current of 950mA.Nail is knocked in battery with method same as Example 1, and the battery temperature after 90 seconds is assessed.It the results are shown in Table 6.
Table 4
| Battery | Porous heat-resistant layer (μm) | The position of porous heat-resistant layer | Diaphragm (μm) | Filler | Binder content (wt%) | Porosity (%) |
| 31 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 32 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 33 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 34 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 35 | 5 | Cathode | 10 | Aluminium oxide | 3 | 50 |
| 36 | 5 | Anode | 10 | Aluminium oxide | 3 | 50 |
| 37 | 5 | Anode | 10 | Aluminium oxide | 3 | 50 |
| 38 | 15 | Cathode | Nothing | Aluminium oxide | 3 | 50 |
| 39 | 5 | Cathode | 10 | Magnesia | 3 | 50 |
| 40 | 5 | Cathode | 10 | Silica | 3 | 50 |
| 41 | 5 | Cathode | 10 | Titanium dioxide | 3 | 50 |
| 42 | 5 | Cathode | 10 | Zirconium oxide | 3 | 50 |
| 43 | 5 | Diaphragm | 10 | Aromatic polyamides | - | 48 |
| 44 | 5 | Diaphragm | 10 | Polyamidoimide | - | 47 |
| 45 | 15 | Independent thin slice | Nothing | Aromatic polyamides | - | 51 |
| 46 | 15 | Independent thin slice | Nothing | Polyamidoimide | - | 52 |
| 47 | 5 | Cathode | 10 | Aluminium oxide | 0.5 | 61 |
| 48 | 5 | Cathode | 10 | Aluminium oxide | 1 | 57 |
| 49 | 5 | Cathode | 10 | Aluminium oxide | 10 | 42 |
| 50 | 5 | Cathode | 10 | Aluminium oxide | 20 | 35 |
| 51 | 5 | Cathode | 10 | Aluminium oxide | 3 | 30 |
| 52 | 5 | Cathode | 10 | Aluminium oxide | 3 | 42 |
| 53 | 5 | Cathode | 10 | Aluminium oxide | 3 | 60 |
| 54 | 5 | Cathode | 10 | Aluminium oxide | 3 | 78 |
| 55 | 5 | Cathode | 10 | Aluminium oxide | 3 | 89 |
| 56 | Nothing | - | 15 | - | - | - |
| 57 | Nothing | - | 15 | - | - | - |
| 58 | Nothing | - | 15 | - | - | - |
| 59 | Nothing | - | 15 | - | - | - |
| 60 | Nothing | - | 15 | - | - | - |
Table 5
| Battery | Cathode width B (mm) | Positive width (mm) | Design capacity (mAh) | B/A |
| 31 | 43.7 | 42.7 | 950 | 0.950 |
| 32 | 44.6 | 43.6 | 970 | 0.970 |
| 33 | 45 | 44 | 979 | 0.978 |
| 34 | 45.7 | 44.7 | 994 | 0.993 |
| 35 | 46.5 | 45.5 | 1012 | 1.011 |
| 36 | 45 | 44 | 979 | 0.978 |
| 37 | 45.7 | 44.7 | 994 | 0.993 |
| 38 | 45 | 44 | 979 | 0.978 |
| 39 | 45 | 44 | 979 | 0.978 |
| 40 | 45 | 44 | 979 | 0.978 |
| 41 | 45 | 44 | 979 | 0.978 |
| 42 | 45 | 44 | 979 | 0.978 |
| 43 | 45 | 44 | 979 | 0.978 |
| 44 | 45 | 44 | 979 | 0.978 |
| 45 | 45 | 44 | 979 | 0.978 |
| 46 | 45 | 44 | 979 | 0.978 |
| 47 | 45 | 44 | 979 | 0.978 |
| 48 | 45 | 44 | 979 | 0.978 |
| 49 | 45 | 44 | 979 | 0.978 |
| 50 | 45 | 44 | 979 | 0.978 |
| 51 | 45 | 44 | 979 | 0.978 |
| 52 | 45 | 44 | 979 | 0.978 |
| 53 | 45 | 44 | 979 | 0.978 |
| 54 | 45 | 44 | 979 | 0.978 |
| 55 | 45 | 44 | 979 | 0.978 |
| 56 | 43.7 | 42.7 | 950 | 0.950 |
| 57 | 44.6 | 43.6 | 970 | 0.970 |
| 58 | 45 | 44 | 979 | 0.978 |
| 59 | 45.7 | 44.7 | 994 | 0.993 |
| 60 | 46.5 | 45.5 | 1012 | 1.011 |
Table 6
| Battery | Short-circuit incidence (%) | Resistance to falling impacts (%) | Short-circuit incidence (%) after falling | High output characteristic (%) | Battery temperature (DEG C) after nail punctures |
| 31 | 0 | 93.3 | 1 | 90.4 | 83 |
| 32 | 0 | 98.0 | 0 | 91.2 | 86 |
| 33 | 0 | 99.9 | 0 | 90.1 | 80 |
| 34 | 0 | 99.7 | 0 | 89.4 | 82 |
| 35 | 20 | 98.8 | 0 | 88.9 | 83 |
| 36 | 4 | 99.8 | 3 | 90.2 | 86 |
| 37 | 11 | 99.7 | 12 | 91.3 | 86 |
| 38 | 2 | 99.8 | 13 | 87.8 | 93 |
| 39 | 0 | 99.7 | 0 | 89.1 | 86 |
| 40 | 0 | 99.9 | 0 | 90.1 | 86 |
| 41 | 0 | 99.8 | 0 | 88.9 | 82 |
| 42 | 0 | 99.8 | 0 | 90.4 | 84 |
| 43 | 0 | 99.6 | 10 | 88.8 | 82 |
| 44 | 0 | 99.7 | 11 | 90.1 | 84 |
| 45 | 0 | 99.8 | 12 | 91.2 | 85 |
| 46 | 0 | 99.9 | 11 | 90.7 | 82 |
| 47 | 0 | 99.9 | 8 | 90.4 | 87 |
| 48 | 0 | 99.8 | 0 | 91.4 | 82 |
| 49 | 0 | 99.7 | 0 | 85.3 | 81 |
| 50 | 0 | 99.9 | 0 | 80.3 | 78 |
| 51 | 0 | 96.0 | 0 | 87.7 | 83 |
| 52 | 0 | 99.8 | 0 | 88.2 | 88 |
| 53 | 0 | 100.0 | 0 | 89.4 | 81 |
| 54 | 0 | 99.7 | 0 | 90.0 | 85 |
| 55 | 2 | 99.8 | 14 | 92.1 | 94 |
| 56 | 0 | 99.7 | 0 | 88.4 | 126 |
| 57 | 15 | 99.9 | 0 | 88.9 | 123 |
| 58 | 20 | 99.8 | 0 | 90.2 | 131 |
| 59 | 28 | 99.8 | 0 | 89.1 | 124 |
| 60 | 48 | 99.8 | 5 | 90.1 | 130 |
Opposite from the battery 31 too small to the distance A of battery case inner bottom surface of insulator (restriction site) lower surface in cathode width B, capacity density is smaller, and furthermore resistance to falling impacts are lower.After drop test, battery 31 is dismantled and is observed, as a result, it has been found that movement has occurred in the electrode of winding electrode assembly.
Battery 31 is because the effect of porous heat-resistant layer is without internal short-circuit, but the reduction of effective area (anode and cathode area relative to each other) leads to its capacitance loss.Because being furnished with porous heat-resistant layer, electrode assembly is anti-deformation, therefore its inside that cannot be firmly secured to battery case.Therefore the electrode for winding electrode assembly may be moved when repeating to fall.
On the other hand, opposite from the battery 35 excessive to the distance A of battery case inner bottom surface of insulator lower surface in cathode width B, resistance to short-circuit is lower.The sample for determining the battery 35 in internal short-circuit state is dismantled and is observed.As a result, it has been found that the porous heat-resistant layer in negative terminal surface has damage in the upper half of electrode assembly.It has also been found that diaphragm cracks.
In the battery 33~34 that the ratio of B/A is 0.975~0.995, resistance to short-circuit is higher, and furthermore resistance to falling impacts are improved.Battery of the invention is also equipped with porous heat-resistant layer in addition to having diaphragm.Therefore, even if making deformed part insulate by the double-layer structure that porous heat-resistant layer and diaphragm form when cathode is wider than anode, there is slight deformation in the electrode assembly upper half.Further, since the ratio of B/A is higher, electrode assembly is firmly sandwiched between the surface of insulator lower half and the inner bottom surface of battery case.Therefore the resistance to falling impacts of battery may be improved.
However, B/A ratio be 0.965~0.975 battery 32 in, resistance to falling impacts be slightly below have same ratio range B/A cylindrical battery 2 (embodiment 1) resistance to falling impacts.For cylindrical battery, the cross section of step (restriction site) is approximate V-arrangement or U-shaped.Therefore, the top of electrode assembly is pushed down by the slope of step.On the other hand, for square lithium secondary battery, the surface of insulator (restriction site) lower half is flat, therefore without the slope as step.Therefore various batteries may be in more efficiently B/A ratio range and there are above-mentioned differences.
In the battery 56~60 of not porous heat-resistant layer, the influence of the resistance to unrestricted site location of falling impacts is excellent.It is believed that the electrode assembly because of not no porous heat-resistant layer is deformed to an appropriate level, therefore it is firmly secured in battery case.Even if causing the electrode movement of the winding electrode assembly of capacitance loss that may therefore be suppressed when these batteries fall.However, these batteries 56~60 obviously overheat in nail puncture test.In addition, resistance to short-circuit is lower in restriction site position respectively battery 57~59 identical with battery 32~34.It is believed that the cathode of these batteries 57~59 has slight deformation.However, when diaphragm cracks because of cathode deformation, internal short-circuit cannot prevent since these batteries do not have porous heat-resistant layer.
In battery 36 and 37, porous heat-resistant layer is formed on the surface of anode active material layer.In both batteries, the battery 37 with wider cathode shows relatively low resistance to short-circuit.This may be because porous heat-resistant layer is formed on the surface of the anode active material layer more narrower than anode active material layer, and then negative terminal surface is touched in the upper half of electrode assembly and the upper half side edge of anode.
In not having septate battery 38, the resistance to short-circuit of lower backwardness is slightly lower.It is more more fragile than diaphragm in porous heat-resistant layer structure.Then, porous heat-resistant layer is acted on and local damage by falling impacts, so that short circuit occur.
In the battery 43 and 44 that membrane surface has the porous heat-resistant layer made of heat stable resin, the resistance to short-circuit of lower backwardness is slightly lower.The mechanical strength of porous heat-resistant layer made of heat stable resin is lower than the mechanical strength of the porous heat-resistant layer comprising insulating packing and adhesive.Then, short circuit is acted on by falling impacts and being occurred.
With independent porous heat-resistant layer thin slice and do not having in septate battery 45 and 46, they fall after resistance to short-circuit fallen lower than battery 43 and battery 44 after resistance to short-circuit.This is derived from the fact, i.e. the intensity of porous heat-resistant layer intensity difference and porous heat-resistant layer made of heat stable resin is not improved because of lacking for diaphragm.
In porous heat-resistant layer in the battery 47 of the adhesive containing 0.5wt%, the resistance to short-circuit after falling is slightly lower.This may be the adhesion strength that filler grain is reduced because of the adhesive of low content, poor so as to cause the mechanical strength of porous heat-resistant layer.
On the other hand, in the battery 50 containing 20wt% adhesive, high output characteristic is slightly lower.This may be because excessive adhesive reduces the porosity of porous heat-resistant layer, in addition, excessive adhesive is swollen with electrolyte, to make the micropore of porous heat-resistant layer be closed and reduce ionic conductivity.On the other hand, in the battery 48~49 that binder content is 1wt%~10wt%, resistance to short-circuit and high output characteristic are all excellent.
In the battery 51 of the porous heat-resistant layer with 30% porosity obtained by control drying condition, resistance to falling impacts are slightly lower.Its reason may be as follows.Since porosity is low, porous heat-resistant layer is not sufficiently wet electrolyte, and then the swelling of electrode assembly is smaller.It is thus impossible to prevent electrode assembly mobile when falling.In the battery 55 of the porous heat-resistant layer with 89% porosity, the resistance to short-circuit after falling is slightly lower.This may be because the mechanical strength of porous heat-resistant layer is poor.
On the other hand, in the battery 52~54 for the porous heat-resistant layer for being 40%~80% with porosity, resistance to falling impacts are excellent with the resistance to short-circuit after falling.Its reason may be as follows.Due to optimized porosity, the mechanical strength of porous heat-resistant layer is maintained.In addition, porous heat-resistant layer swells to an appropriate level with electrolyte.It has been then prevented from the movement of electrode assembly.
Industrial applicibility
Since lithium secondary battery of the invention has outstanding resistance to shorting and heat resistance and high security and will not have capacitance loss because impact is as fallen, therefore it can be used as the power supply of any mancarried device, such as personal digital assistant and portable electronic device.Lithium secondary battery of the invention can be used as the power supply such as home-use small-sized electrical storage device, two-wheeled vehicle, electric vehicle and dual-purpose electric vehicle, and purposes of the invention is not particularly limited.
(according to the 19th article of modification of treaty)
A kind of (1. modification) lithium secondary battery, comprising: have bottom, side wall and open-topped battery case；Electrode assembly；Nonaqueous electrolytic solution；And open-topped sealing plate to accommodate the battery case of the electrode assembly and the electrolyte is covered,
It is characterized in that, the electrode assembly includes the bar shaped anode and bar shaped cathode being intertwined with the porous heat-resistant layer of insertion between a positive electrode and a negative electrode, the anode includes positive core components and the anode active material layer being coated on positive core components two sides, the cathode includes cathode core components and the anode active material layer that is coated on cathode core components two sides
The battery, which has, limits the restriction site that the electrode assembly vertically moves, and meets relational expression: 0.965≤B/A≤0.995 from the restriction site to the distance A of the battery case inner bottom surface and the width B of the cathode,
The porous heat-resistant layer contains insulating packing and adhesive, and
The porous heat-resistant layer has 40%~80% porosity.
2. lithium secondary battery as described in claim 1, which is characterized in that further comprise the diaphragm containing microporous barrier, the diaphragm is inserted between the porous heat-resistant layer and the anode or between the porous heat-resistant layer and the cathode.
3. lithium secondary battery as described in claim 1, which is characterized in that the porous heat-resistant layer is formed on the surface of at least one in the anode active material layer and the anode active material layer.
(4. deletion)
(5. modification) lithium secondary battery as described in claim 1, which is characterized in that the insulating packing includes inorganic oxide.
6. lithium secondary battery as claimed in claim 5, which is characterized in that the inorganic oxide includes selected from least one of aluminium oxide, silica, magnesia, titanium dioxide and zirconium oxide.
(7. modification) lithium secondary battery as described in claim 1, which is characterized in that on the basis of the insulating packing of 100 parts by weight, the amount of the adhesive is 1~10 parts by weight.
(8. deletion)
9. lithium secondary battery as described in claim 1, which is characterized in that the electrode assembly is substantially cylindrical, and the battery case is cylindrical shape, and the restriction site is the groove portion of the battery case for reducing internal diameter positioned at battery case side wall upper part.
10. lithium secondary battery as described in claim 1, it is characterized in that, the insulator between the electrode assembly and the sealing plate is further included, wherein the electrode assembly is substantially elliptical cylinder, the electrode assembly be it is prismatic, the restriction site is the lower surface of insulator.
11. lithium secondary battery as claimed in claim 10, which is characterized in that meet relational expression: 0.975≤B/A≤0.995 from the restriction site to the distance A of the inner surface of the battery case bottom and the width B of the cathode.
Claims (11)
1. a kind of lithium secondary battery, comprising: have bottom, side wall and open-topped battery case；Electrode assembly；Nonaqueous electrolytic solution；And open-topped sealing plate to accommodate the battery case of the electrode assembly and the electrolyte is covered,
It is characterized in that, the electrode assembly includes the bar shaped anode and bar shaped cathode being intertwined with the porous heat-resistant layer of insertion between a positive electrode and a negative electrode, the anode includes positive core components and the anode active material layer being coated on positive core components two sides, the cathode includes cathode core components and the anode active material layer that is coated on cathode core components two sides, and
The battery, which has, limits the restriction site that the electrode assembly vertically moves, and meets relational expression: 0.965≤B/A≤0.995 from the restriction site to the distance A of the battery case bottom interior surface and the width B of the cathode.
2. lithium secondary battery as described in claim 1, which is characterized in that further comprise the diaphragm containing microporous barrier, the diaphragm is inserted between the porous heat-resistant layer and the anode or between the porous heat-resistant layer and the cathode.
3. lithium secondary battery as described in claim 1, which is characterized in that the porous heat-resistant layer is formed on the surface of at least one in the anode active material layer and the anode active material layer.
4. lithium secondary battery as described in claim 1, which is characterized in that the porous heat-resistant layer contains insulating packing and adhesive.
5. lithium secondary battery as claimed in claim 4, which is characterized in that the insulating packing includes inorganic oxide.
6. the lithium secondary battery as described in patent requirements 5, which is characterized in that the inorganic oxide includes selected from least one of aluminium oxide, silica, magnesia, titanium dioxide and zirconium oxide.
7. lithium secondary battery as claimed in claim 4, which is characterized in that on the basis of the insulating packing of 100 parts by weight, the amount of described adhesive is 1~10 parts by weight.
8. lithium secondary battery as claimed in claim 4, which is characterized in that the porous heat-resistant layer has 40%~80% porosity.
9. lithium secondary battery as described in claim 1, which is characterized in that the electrode assembly is substantially cylindrical, and the battery case is cylindrical shape, and the restriction site is the groove portion of the battery case for reducing internal diameter positioned at the battery case side wall upper part.
10. lithium secondary battery as described in claim 1, it is characterized in that, further comprising the insulator between the electrode assembly and the sealing plate, wherein the electrode assembly is substantially elliptical cylinder, the battery case be it is prismatic, the restriction site is the lower surface of insulator.
11. lithium secondary battery as claimed in claim 10, which is characterized in that meet relational expression: 0.975≤B/A≤0.995 from the restriction site to the distance A of the inner surface of the battery case bottom and the width B of the cathode.
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