JP2012160292A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which is excellent in cycle characteristic.SOLUTION: The nonaqueous electrolyte secondary battery stores, in a bottomed cylindrical armor, a nonaqueous electrolyte containing nonaqueous solvent and electrolyte salt as well as a winding electrode body on which a positive electrode plate, in which a positive electrode active material layer is formed in a band-like positive electrode core body, a negative electrode plate, in which a negative electrode active material layer is formed in a band-like negative electrode core body, and a separator which separates the positive electrode plate from the negative electrode plate. A porous layer containing inorganic particles is formed on an active material layer of at least one of the positive electrode active material layer and the negative electrode active material layer. The following conditions are established: 3≤x≤5, and 1≤y<x, where x is thickness at a winding center side end part of the porous layer and y is thickness at a winding terminal side end part of the porous layer. The thickness of the porous layer reduces gradually from the winding center side end part toward the winding terminal side end part.

Description

  The present invention relates to an improvement in a non-aqueous electrolyte secondary battery.

  In recent years, mobile information terminals such as mobile phones and notebook personal computers have been rapidly advanced in function, size and weight. As a driving power source for these terminals, non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries having high energy density and high capacity are widely used.

  Non-aqueous electrolyte secondary batteries are required to have higher capacities, and in order to meet this demand, the active material filling density of the positive electrode and the negative electrode is increased. However, when the active material packing density is increased, the void volume in the electrode is reduced accordingly, and the nonaqueous electrolytic mass retained in the electrode is reduced. When the non-aqueous electrolysis mass shortage occurs in the electrode, charging / discharging does not proceed smoothly in the region where the non-aqueous electrolysis mass is insufficient, and a large current flows locally in the region where the non-aqueous electrolysis mass is not insufficient. It will be. Thus, when current imbalance occurs in the electrode plate, lithium tends to precipitate on the surface of the electrode plate or the active material is likely to be deteriorated, so that there is a problem that charge / discharge cycle characteristics are deteriorated. .

  Here, the following patent documents 1-4 are mentioned as a technique regarding a nonaqueous electrolyte battery.

JP 2009-38016 A JP 2006-12703 JP-A-9-80704 JP 2007-172880 JP

  Patent Document 1 discloses an electrode plate having a long core material, a mixture layer formed thereon, and an exposed portion of the core material provided along one side parallel to the longitudinal direction of the core material. In this technique, a porous film is formed at least in the vicinity of the end face of the mixture layer and at the mixture layer in the exposed portion of the core material. According to this technology, it is said that a non-aqueous electrolyte secondary battery that can maintain high reliability can be obtained even when displacement between the positive electrode and the negative electrode occurs due to vibration or the like.

  Patent Document 2 uses positive and negative electrode plates in which the thickness of the mixture layer is larger than the inside of the electrode group and the bulk density of the mixture layer is substantially uniform, and the current collecting tab is formed from the end face of the electrode group. This is a technique using an electrode group derived one by one for a certain length of the current collector. According to this technique, a secondary battery capable of achieving both high output and high capacity is obtained.

  Patent Document 3 is a technique in which the amount of electrode material applied to at least one surface of at least one electrode sheet of a positive electrode sheet and a negative electrode sheet is changed in the electrode sheet length direction. According to this technology, it is said that a battery having high capacity, good cycle characteristics, and high safety can be obtained.

  Patent Document 4 forms a thick portion in the positive electrode plate and the negative electrode plate, both of which are thicker than the other end side at one end side in the width direction in the cross section parallel to the short side, In addition, the positive electrode plate and the negative electrode plate are techniques that are arranged so that the thick portions are located on opposite sides. According to this technique, it can be said that winding of the positive electrode plate and the negative electrode plate can be prevented.

  However, the techniques according to Patent Documents 1 to 4 cannot sufficiently improve cycle characteristics.

  This invention is made | formed in view of the above, Comprising: It aims at providing the nonaqueous electrolyte secondary battery excellent in cycling characteristics.

  In order to solve the above problems, the present invention provides a positive electrode plate in which a positive electrode active material layer is formed on a belt-like positive electrode core, a negative electrode plate in which a negative electrode active material layer is formed on a belt-like negative electrode core, and the positive electrode plate And a separator separating the negative electrode plate, a wound electrode body wound, and a nonaqueous electrolyte having a nonaqueous solvent and an electrolyte salt are housed in a bottomed cylindrical outer package In the secondary battery, a porous layer having inorganic particles is formed on at least one of the positive electrode active material layer and the negative electrode active material layer, and a winding center side end of the porous layer is formed. Where x is the thickness at the part and y is the thickness at the winding end side end of the porous layer, 3 ≦ x ≦ 5 and 1 ≦ y <x are satisfied, and the thickness of the porous layer is It is characterized by decreasing from the winding center side end toward the winding end side end.

  In the case of a battery using a wound electrode body, a larger winding pressure is applied to the winding start side (winding center side) than the winding end side (winding end side), and the voids in the active material layer are further reduced by the winding pressure. Therefore, the above non-aqueous electrolyte shortage is more likely to occur on the winding start side.

  Here, when the porous layer is formed on the surface of the active material layer of the positive electrode or the negative electrode, the porous layer favorably holds the nonaqueous electrolyte, and has the action of supplying the held nonaqueous electrolyte to the active material layer. A shortage of non-aqueous electrolyte can be prevented. As the thickness of the porous layer increases, the non-aqueous electrolytic mass that can be retained increases. However, since the porous layer itself does not directly participate in the charge / discharge reaction, if the thickness is increased too much, the discharge capacity decreases.

  In the configuration of the present invention, the thickness of the porous layer is such that the winding center side end> the winding end side end, and the thickness decreases toward the winding end side end. Therefore, the balance of the amount of nonaqueous electrolyte supplied from the winding center to the winding end is well maintained. Thereby, current imbalance in the electrode plate can be prevented without increasing the total volume of the porous layer. That is, it is possible to suppress the precipitation of lithium and the deterioration of the active material without sacrificing the discharge capacity, and to remarkably improve the cycle characteristics.

  Here, in order to hold a sufficient amount of the non-aqueous electrolyte on the winding center side where the winding pressure acts greatly, the thickness of the porous layer at the winding center side end is set to 3 μm or more. Further, in order to retain a sufficient amount of the nonaqueous electrolyte on the winding end side where the acting winding pressure is small, the thickness of the porous layer at the winding end side end is set to 1 μm or more. From the viewpoint of preventing the discharge capacity from decreasing, the upper limit of the thickness of the porous layer is 5 μm.

  The porous layer provided on the positive electrode side supplies the retained nonaqueous electrolyte not only to the positive electrode side, but also to the negative electrode side disposed oppositely, and the porous layer provided on the negative electrode side provides the retained nonaqueous electrolyte. Is supplied not only to the negative electrode side but also to the positive electrode side. Therefore, the porous layer may be provided on either the positive or negative electrode plate, or may be provided on both. When provided on both sides, the total of the porous provided on both sides is preferably 5 μm or less.

  In addition, the thickness distribution of the porous layer may change continuously or discontinuously.

  In the porous layer, inorganic particles are included as an essential component, but in addition to this, a binder and other additives may be included. In addition, it is preferable that the material constituting the porous layer is an insulating material because the porous layer also acts to prevent a short circuit between the positive and negative electrodes in addition to the separator.

  The inorganic particles preferably include at least one selected from the group consisting of aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, and silicon oxide. More specifically, alumina, titania, magnesia, zirconia, silica, or the like can be used. The average particle size of the inorganic particles is preferably 0.1 to 1.0 μm.

  Moreover, in order for a porous layer to hold | maintain a non-aqueous electrolyte favorably, it is preferable that the porosity of a porous layer shall be 30-80%.

  Further, when the charge potential of the positive electrode is increased in order to increase the discharge capacity, the nonaqueous electrolytic mass per discharge capacity tends to be insufficient. However, since the non-aqueous electrolyte shortage can be prevented by adopting the configuration of the present invention, the present invention is applied to a battery in which the potential at the time of charging the positive electrode plate is 4.35 to 4.45 V with respect to lithium. Thus, a nonaqueous electrolyte secondary battery having a large discharge capacity and excellent cycle characteristics can be realized.

  In a battery that performs such high-potential charging, it is preferable to use a carbon material having a charging potential of about 0.1 V based on lithium as the negative electrode active material because a battery with a large amount of electric power can be realized.

  As the carbon-based material, artificial graphite, natural graphite, carbon black, coke, glassy carbon, carbon fiber, or a carbonaceous material such as a fired body thereof can be used.

  On the other hand, non-aqueous electrolyte secondary batteries using a negative electrode active material containing silicon or tin, which has a higher lithium reference potential than graphite, and other alloys and oxides, use the positive electrode active material to a higher potential in order to increase the battery voltage. Sometimes. Therefore, even if it is such a nonaqueous electrolyte secondary battery, the effect of this invention is acquired similarly to what used the carbonaceous material for the negative electrode active material.

  In addition, the present invention provides a non-aqueous electrolyte secondary filled with a high density (which tends to cause a shortage of non-aqueous electrolyte) such that it is filled at a packing density of 70% or more of the true density of the active material calculated by the X-ray diffraction method. When applied to a battery, the effect is more prominent.

  According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery having a uniform non-aqueous electrolyte retention amount of the wound electrode body, and thereby excellent cycle characteristics.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated in detail using an Example.

Example 1
<Preparation of positive electrode>
Cobalt carbonate was pyrolyzed at 550 ° C. to obtain tricobalt tetroxide (Co ₃ O ₄ ). Lithium carbonate (Li ₂ CO ₃ ) as a lithium source was mixed with this so that the molar ratio of Co and Li was 1: 1, and calcined at 850 ° C. for 20 hours in an air atmosphere to obtain lithium cobalt oxide. (LiCoO ₂ ) was obtained. This was pulverized with a mortar so that the average particle size was 15 μm.

  The lithium cobaltate, carbon powder as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder are mixed in a mass ratio of 96: 2: 2, and these are mixed with N-methyl-2- A positive electrode active material slurry was prepared by mixing with pyrrolidone (NMP).

  Next, using a doctor blade, this positive electrode active material slurry was applied to both surfaces of a positive electrode core made of a strip-shaped aluminum foil (thickness: 15 μm) with a uniform thickness. At this time, the length of the active material application part was 550 mm, and the length of the active material non-application part was 75 mm. This electrode plate was passed through a drier to remove the organic solvent (NMP) used at the time of slurry preparation to produce a dry electrode plate. The dried electrode plate was rolled using a roll press so that the thickness was 160 μm, and cut into a predetermined size to obtain a positive electrode plate.

<Production of negative electrode>
Graphite powder as a negative electrode active material, styrene butadiene rubber as a binder, and carboxymethyl cellulose as a thickener are mixed in a mass ratio of 97.5: 1.5: 1, and these are mixed with water. The negative electrode active material slurry was prepared by mixing.

  Next, this negative electrode active material slurry was applied with a uniform thickness on both surfaces of a negative electrode core made of a strip-shaped copper foil (thickness: 10 μm) using a doctor blade. At this time, the length of the active material application part was 590 mm, and the length of the active material non-application part was 60 mm. The electrode plate was passed through a drier to remove the water used during slurry preparation, and a dried electrode plate was produced. Then, this dry electrode plate was rolled with a roll press so that the thickness was 145 μm, and cut into a predetermined size to obtain a negative electrode plate.

  In addition, the electric potential at the time of charge of graphite is about 0.1 V on the basis of lithium, and the amount of active material of the positive electrode plate and the negative electrode plate is the electric potential of the positive electrode active material which is a design standard (in this example, 4.40 V on the basis of lithium). ), The charge capacity ratio between the positive electrode and the negative electrode (negative electrode charge capacity / positive electrode charge capacity) was adjusted to 1.1. Here, the charge capacity ratio is preferably in the range of 1.0 to 1.1.

<Formation of porous layer>
Aluminum oxide (AKP3000 manufactured by Sumitomo Chemical Co., Ltd.), carboxymethylcellulose (# 1380 manufactured by Daicel Chemical Industries, Ltd.) and pure water are mixed at a mass ratio of 30.0: 0.5: 69.5 (HIMIX made by PRIMIX) ) And kneaded. The obtained slurry was dispersed using a bead mill (Nanomill dispersing apparatus manufactured by Asada Tekko). The dispersion conditions were an internal volume of 0.3 L, a bead diameter of 0.5 mm, a slit of 0.15 mm, a bead filling amount of 90%, a peripheral speed of 40 Hz, and a treatment flow rate of 1.5 kg / min. After that, 3.75% by mass of acrylic rubber binder with respect to the mass of aluminum oxide and pure water were added so that the mass ratio of aluminum oxide would be 30% by mass and kneaded by the kneader. .

  The dispersion slurry was applied on the positive electrode active material layer of the positive electrode plate by a dip coating method. At this time, the region from the start of winding to 100 mm has 5 dip times, the region from 100 to 200 mm has 4 dip times, the region from 200 to 300 mm has 3 dip times, and the region from 300 to 400 mm has 3 dip times. The number of dip times was 2, and the region from 400 mm to the end of winding was set to 1 dip, and the thickness of the porous layer was 3 μm at the start of winding and 1 μm at the end of winding.

<Production of electrode body>
An aluminum lead was welded to the positive electrode plate on which the porous layer was formed, and a nickel lead was welded to the negative electrode plate. After that, the positive electrode plate, the negative electrode plate, and a separator (thickness 22 μm) made of polyethylene are overlapped, wound by a winder, and provided with an insulating winding tape to complete a wound electrode body. It was.

<Preparation of non-aqueous electrolyte>
LiPF ₆ as an electrolyte salt is added to a non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 3: 7 (when converted to 1 atm and 25 ° C.). A non-aqueous electrolyte was obtained by dissolving at a rate of 0 M (mol / liter).

<Battery assembly>
Insulating plates were respectively arranged on the upper and lower surfaces of the wound electrode body, the electrode body was inserted into a bottomed cylindrical outer can, and the positive electrode lead was welded to the sealing plate and the negative electrode lead was welded to the outer can. After that, the nonaqueous electrolyte was injected into the outer can in a glow box filled with Ar. After that, the sealing plate was caulked and fixed using an insulating gasket to produce a nonaqueous electrolyte secondary battery according to Example 1 having a diameter of 18 mm, a height of 65 mm, and a design capacity of 2.2 Ah.

(Example 2)
A battery according to Example 2 was fabricated in the same manner as in Example 1 except that the thickness of the porous layer was 4 μm at the beginning of winding and 1 μm at the end of winding.

(Example 3)
A battery according to Example 3 was fabricated in the same manner as in Example 1 except that the thickness of the porous layer was 5 μm at the beginning of winding and 1 μm at the end of winding.

Example 4
Implementation was carried out in the same manner as in Example 1 except that a positive electrode plate having no porous layer was used and a negative electrode plate having a porous layer formed on the negative electrode active material layer by the following method was used. A battery according to Example 4 was produced.

<Formation of porous layer>
Aluminum oxide (AKP3000 manufactured by Sumitomo Chemical), polyvinylidene fluoride (PVdF), and N-methyl-2-pyrrolidone (NMP) at a mass ratio of 30.0: 69.5: 0.5 The mixture was introduced into PRIMIX Hibismix) and kneaded. The obtained slurry was dispersed using a bead mill (Nanomill dispersing apparatus manufactured by Asada Tekko). The dispersion conditions were an internal volume of 0.3 L, a bead diameter of 0.5 mm, a slit of 0.15 mm, a bead filling amount of 90%, a peripheral speed of 40 Hz, and a treatment flow rate of 1.5 kg / min.

  The dispersion slurry was applied to the negative electrode plate by a dip coating method. At this time, the region from the start of winding to 100 mm has 5 dip times, the region from 100 to 200 mm has 4 dip times, the region from 200 to 300 mm has 3 dip times, and the region from 300 to 400 mm has 3 dip times. The number of dip times was 2, and the region from 400 mm to the end of winding was set to 1 dip, and the thickness of the porous layer was 3 μm at the start of winding and 1 μm at the end of winding.

(Example 5)
A battery according to Example 5 was fabricated in the same manner as in Example 4 except that the thickness of the porous layer was 4 μm at the start of winding and 1 μm at the end of winding.

(Example 6)
A battery according to Example 6 was made in the same manner as in Example 4 except that the thickness of the porous layer was 5 μm at the beginning of winding and 1 μm at the end of winding.

(Comparative Example 1)
A battery according to Comparative Example 1 was produced in the same manner as in Example 1 except that a positive electrode plate without a porous layer was used.

(Comparative Example 2)
A battery according to Comparative Example 2 was fabricated in the same manner as in Example 1 except that the thickness of the porous layer was 1 μm at the beginning of winding and 3 μm at the end of winding. At this time, the region from the start of winding to 100 mm has one dip, the region from 100 to 200 mm has two dips, the region from 200 to 300 mm has three dips, the region from 300 to 400 mm The number of dip times was 4, and the number of dip times was 5 in the region from 400 mm to the end of winding.

(Comparative Example 3)
A battery according to Comparative Example 3 was fabricated in the same manner as in Example 1 except that the thickness of the porous layer was 2 μm in all regions. At this time, the number of dips was set to 3 in all the areas.

(Comparative Example 4)
A battery according to Comparative Example 4 was produced in the same manner as in Example 4 except that the thickness of the porous layer was 1 μm at the beginning of winding and 3 μm at the end of winding. At this time, the region from the start of winding to 100 mm has one dip, the region from 100 to 200 mm has two dips, the region from 200 to 300 mm has three dips, the region from 300 to 400 mm The number of dip times was 4, and the number of dip times was 5 in the region from 400 mm to the end of winding.

(Comparative Example 5)
A battery according to Comparative Example 5 was produced in the same manner as in Example 4 except that the thickness of the porous layer was 2 μm in all regions. At this time, the number of dips was set to 3 in all the areas.

[Charge / discharge cycle test]
Batteries were produced under the same conditions as in Examples 1 to 6 and Comparative Examples 1 to 5, and these batteries were charged and discharged under the following conditions, and the capacity remaining rate was calculated according to the following formula. In addition, all this charging / discharging was performed on 25 degreeC conditions. The results are shown in Table 1 below. In addition, all this charging / discharging was performed on 25 degreeC conditions.

Charging: constant current 0.5 It (1.1 A) until voltage reaches 4.3 V, then constant voltage 4.3 V until current reaches 0.02 It (44 mA): constant current 1 It (2.2 A) Capacity retention rate (%) until the voltage reaches 3.0V = 500th cycle discharge capacity / first cycle discharge capacity × 100

  From Table 1 above, in Examples 1 to 6, in which the thickness of the porous layer is 3 to 5 μm at the start of winding and 1 μm at the end of winding, the capacity retention rate after 500 charge / discharge cycles is 75 to 80%. On the other hand, Comparative Example 1 in which the porous layer is not provided, and Comparative Examples 2 to 5 in which the thickness of the porous layer at the beginning of winding is 1 to 2 μm have a capacity retention rate of 45 to 55%, and Examples 1 to It can be seen that 6 is better.

  This is considered as follows. When a sufficient amount of non-aqueous electrolyte is not supplied to the active material, charging / discharging does not proceed smoothly in a portion where the non-aqueous electrolytic mass is insufficient, and a large current flows locally in other portions. Thereby, lithium is easily deposited on the negative electrode surface, and the active material is easily deteriorated. In the wound electrode body, the winding pressure acts more on the winding start (winding center) side, and the non-aqueous electrolytic mass on the winding start side becomes smaller than that on the winding end (winding end) side. In particular, a shortage of non-aqueous electrolyte is likely to occur on the side. Here, the porous layer formed on the surface of the positive electrode or the negative electrode has a property of favorably holding the non-aqueous electrolyte, and the non-aqueous electrolyte held in the porous layer is supplied to the electrode. There is an effect to prevent shortage.

  As in Examples 1 to 6, if the thickness distribution of the porous layer is restricted to a configuration in which the winding start end portion> the winding end end portion and the thickness decreases from the winding start to the winding end. Since the supply amount balance of the nonaqueous electrolyte in the electrode is kept good, the charge / discharge cycle proceeds smoothly, and the capacity retention rate thereafter can be significantly increased. In Comparative Examples 2 to 5 in which the thickness of the porous layer is the winding start ≦ the winding end, and in Comparative Example 1 in which the porous layer is not formed, the supply amount of the nonaqueous electrolyte from the winding start to the winding end is unbalanced. Therefore, the capacity maintenance rate cannot be sufficiently improved.

  Here, in order to hold a sufficient amount of the nonaqueous electrolyte on the winding start side where the winding pressure acts greatly, the thickness of the porous layer at the start of winding is set to 3 μm or more. Further, in order to maintain a sufficient amount of the nonaqueous electrolyte on the winding end side where the acting winding pressure is small, the thickness of the porous layer at the winding end is set to 1 μm or more. In addition, when the thickness of the porous layer is 5 μm or more, the capacity retention rate improvement effect due to the increase in the retained amount of the nonaqueous electrolyte reaches almost the upper limit, and the volume of the porous layer that does not directly contribute to the insertion / desorption of lithium ions is increased. As a result, the volume energy density decreases. Therefore, the upper limit of the thickness of the porous layer is 5 μm.

  Moreover, it turns out that there is no big difference in a capacity | capacitance maintenance factor in Examples 1-3 which provided the porous layer in the positive electrode side, and Examples 4-6 which provided the porous layer in the negative electrode side. Therefore, it was found that the capacity retention ratio can be increased regardless of whether the positive electrode side or the negative electrode side is provided.

(Additions)
As the positive electrode active material, it is preferable to use a lithium transition metal composite oxide, a lithium transition metal phosphate compound having an olivine structure, or the like. Lithium transition metal composite oxide includes lithium cobalt composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, lithium nickel cobalt manganese composite oxide, spinel type lithium manganese composite oxide, and these compounds A compound in which a part of the transition metal element is substituted with another metal element (Zr, Mg, Ti, Al, etc.) is preferable. The lithium transition metal phosphate compound having an olivine structure is preferably lithium iron phosphate. These can be used alone, or can be used in combination of two or more.

  Nonaqueous solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, lactones such as γ-butyrolactone, γ-valerolactone, dimethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, dinormal butyl carbonate, and the like. Chain carbonates, carboxylic acid esters such as methyl pivalate, ethyl pivalate, methyl isobutyrate, methyl propionate, chain ethers such as 1,2-dimethoxyethane, N, N′-dimethylformamide It is preferable to use amides such as N-methyloxazolidinone, sulfur-containing compounds such as sulfolane, and the like, or a mixture thereof.

As the electrolyte salt, LiClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₂ CF ₃ SO ₂ ) ₂ , or the like may be mixed. It is preferable to use it. Moreover, it is preferable that the density | concentration of electrolyte salt shall be 0.5-2.0M (mol / liter).

  As the separator material, polyolefins such as polyethylene, polypropylene, and composite materials thereof can be used. The thickness is preferably 10 to 22 μm and the porosity is preferably 30 to 60%.

  The present invention can also be applied to a polymer electrolyte secondary battery. As the polymer electrolyte, a gel polymer electrolyte is preferable. The polymer component used in the polymer electrolyte is preferably an alkylene oxide polymer or a fluorine polymer such as polyvinylidene fluoride-hexafluoropropylene copolymer.

  As described above, according to the present invention, the nonaqueous electrolytic mass held by the positive and negative electrode plates of the spirally wound electrode body can be made uniform, thereby realizing a nonaqueous electrolyte secondary battery excellent in cycle characteristics. Therefore, industrial applicability is great.

Claims (4)

A positive electrode plate in which a positive electrode active material layer is formed on a belt-like positive electrode core, a negative electrode plate in which a negative electrode active material layer is formed on a belt-like negative electrode core, and a separator that separates the positive electrode plate and the negative electrode plate. In a non-aqueous electrolyte secondary battery in which a wound electrode body wound and a non-aqueous electrolyte having a non-aqueous solvent and an electrolyte salt are housed in a bottomed cylindrical exterior body,
A porous layer having inorganic particles is formed on at least one of the positive electrode active material layer and the negative electrode active material layer,
When the thickness at the winding center side end of the porous layer is x and the thickness at the winding end side end of the porous layer is y, 3 ≦ x ≦ 5 and 1 ≦ y <x are established. And
The thickness of the porous layer decreases from the winding center side end toward the winding end side end,
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 1,
The inorganic particles include at least one selected from the group consisting of aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide, silicon oxide,
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 1 or 2,
The porosity of the porous layer is 30 to 80%.
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 1, 2, or 3,
The potential of the positive electrode plate is 4.35 to 4.45 V with respect to lithium,
A non-aqueous electrolyte secondary battery.