JP2016066426A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having a wound type electrode body, in which the increase in internal resistance of the battery can be suppressed by suppressing the appearance of unevenness in salt concentration of a nonaqueous electrolyte in the electrode body during a high-rate discharge cycle test.SOLUTION: A nonaqueous electrolyte secondary battery 1 comprises: a wound type electrode body 20 in which a negative electrode plate 31 has a negative electrode active material layer 33 including flat graphite particles 35. The negative electrode active material layer 33 has a plurality of oriented parts 33a of which the X-ray diffraction intensity ratio I(110)/I(002) of the graphite particles 35 is 0.04 or more, and at least one of which is oriented part formed in an inside portion 33g; and a plurality of non-oriented parts 33b of which the X-ray diffraction intensity ratio I(110)/I(002) is 0.02 or less and which form portions other than the oriented parts 33a.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a non-aqueous electrolyte secondary battery including a wound electrode body in which a positive electrode plate and a negative electrode plate each having a belt shape are wound through a separator.

  Conventionally, a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as a battery) including a wound electrode body in which a positive electrode plate and a negative electrode plate each having a belt shape are wound through a separator is known. In consideration of being mounted on a vehicle such as a hybrid vehicle or an electric vehicle, for example, in this battery, when a high rate discharge cycle test is performed in which high-rate and short-time discharge and low-rate and long-time charge are repeated, The internal resistance is greatly increased. The reason is that the non-aqueous electrolyte held inside the electrode body expanded by the high-rate discharge flows out from both ends in the axial direction of the electrode body to the outside of the electrode body. At this time, it is considered that the salt concentration of the nonaqueous electrolytic solution inside the electrode body gradually decreases because the nonaqueous electrolytic solution whose salt concentration has temporarily increased due to discharge flows out of the electrode body.

  With respect to this problem, in the battery of Patent Document 1, both the ends in the width direction of the negative electrode active material layer (the axial direction of the electrode body) are applied to the graphite particles in the negative electrode active material layer by applying a magnetic field to the thickness of the negative electrode active material layer. It is set as the site | part orientated to the direction (refer the claim etc. of the cited reference 1). The graphite particles contained at both ends are oriented in a state close to the vertical direction. For this reason, the nonaqueous electrolytic solution retained in the negative electrode active material layer is less likely to move in the width direction of the negative electrode active material layer at both ends as compared with the central portion. This makes it difficult for the non-aqueous electrolyte to flow out from the both end faces in the width direction of the negative electrode active material layer to the outside of the negative electrode active material layer, thereby suppressing an increase in internal resistance when performing a high-rate discharge cycle test.

JP 2013-69579 A

  However, it has been found that the battery of Patent Document 1 may still be insufficient to suppress the increase in internal resistance during the high-rate discharge cycle test. The reason is that the non-aqueous electrolyte retained in the negative electrode active material layer moves in the negative electrode active material layer in the width direction (the axial direction of the electrode body), and the inside of the electrode body (inside the negative electrode active material layer) This is thought to be due to uneven salt concentration of the non-aqueous electrolyte.

  The present invention has been made in view of the current situation, and in a non-aqueous electrolyte secondary battery including a wound electrode body, when a high rate discharge cycle test is performed, non-aqueous electrolysis is performed inside the electrode body. It aims at providing the nonaqueous electrolyte secondary battery which can suppress that the internal resistance of a battery increases by suppressing generating of salt concentration nonuniformity of a liquid.

  One embodiment of the present invention for solving the above problem is a non-aqueous electrolyte secondary battery including a strip-shaped positive electrode plate and a wound electrode body formed by winding a strip-shaped negative electrode plate through a strip-shaped separator. The negative electrode plate has a negative electrode active material layer including flat graphite particles having a strip shape extending in the longitudinal direction of the negative electrode plate and having a dimension smaller in the direction perpendicular to the basal surface than in the spreading direction of the basal surface. The negative electrode active material layer has a strip shape extending in the longitudinal direction and a plurality of alignment portions having an X-ray diffraction intensity ratio I (110) / I (002) of the graphite particles of 0.04 or more. In addition, at least one of the alignment portions is a plurality of alignment portions formed on the inner side of the negative electrode active material layer in the width direction, and the X-ray diffraction intensity ratio I (110) / I (002) is 0.02 or less, and has a plurality of non-oriented parts forming parts other than the oriented parts. A non-aqueous electrolyte solution is a secondary battery.

In this non-aqueous electrolyte secondary battery, the X-ray diffraction intensity ratio I (110) / I (002) (hereinafter also referred to as “orientation strength”) of the graphite particles is 0.04 or more in the negative electrode active material layer. An orientation part is provided. In this orientation portion, the flat graphite particles are oriented in a state close to the vertical direction. For this reason, it is difficult for the non-aqueous electrolyte to move in the width direction of the negative electrode active material layer in the oriented portion as compared to the unoriented portion.
In the present invention, the alignment portion is formed in a plurality of strips extending in the longitudinal direction of the negative electrode plate, and at least one of the alignment portions is formed on the inner side in the width direction of the negative electrode active material layer. Thereby, the non-aqueous electrolyte in the negative electrode active material layer is difficult to move in the width direction on the inner side of the negative electrode active material layer. Therefore, when a high rate discharge cycle test in which a high-rate short-time discharge and a low-rate and long-time charge are repeatedly performed is performed, the non-aqueous electrolyte in the negative electrode active material layer passes through the negative electrode active material layer. By moving in the width direction, it is possible to suppress the occurrence of salt concentration unevenness of the non-aqueous electrolyte inside the electrode body (inside the negative electrode active material layer). And it can suppress that the internal resistance of a battery increases resulting from this salt concentration nonuniformity.

  The “X-ray diffraction intensity ratio I (110) / I (002)” (orientation intensity) is defined as the X-ray diffraction intensity of the (002) plane of the graphite particles with the negative electrode active material layer as the X-ray diffraction measurement surface. This is the intensity ratio when the X-ray diffraction intensity of the I (002) and (110) planes is I (110).

  Further, in the above non-aqueous electrolyte secondary battery, both end portions in the width direction of the negative electrode active material layer may be non-aqueous electrolyte secondary batteries each having the orientation portion.

  In this non-aqueous electrolyte secondary battery, since both end portions in the width direction of the negative electrode active material layer are oriented portions, the non-aqueous electrolyte held in the negative electrode active material layer is in the width direction of the negative electrode active material layer. It becomes difficult to flow out of the negative electrode active material layer from both end surfaces of the negative electrode active material layer. Therefore, the increase in internal resistance when the high rate discharge cycle test is performed can be more effectively suppressed.

  Furthermore, it is a non-aqueous electrolyte secondary battery according to any one of the above, and a plurality of the alignment portions may be non-aqueous electrolyte secondary batteries arranged at regular intervals.

  By arranging a plurality of alignment portions at regular intervals in this way, the alignment portions are arranged in a balanced manner in the negative electrode active material layer, so that the nonaqueous electrolytic solution is inside the electrode body (inside the negative electrode active material layer). It is possible to more effectively suppress the occurrence of uneven salt concentration. Therefore, it can suppress more effectively that the internal resistance of a battery increases.

  Furthermore, in the non-aqueous electrolyte secondary battery according to any one of the above, the width Wb of the unoriented portion is 0.11 ≦ Wb / Wc ≦ with respect to the width Wc of the negative electrode active material layer. A non-aqueous electrolyte secondary battery having a size satisfying 0.43 is preferable.

If the value of the ratio Wb / Wc, which is the ratio of the width Wb of the unoriented portion to the width Wc of the negative electrode active material layer, is too small, specifically smaller than 0.11, the negative electrode active material layer expands during charging. In this case, since the width Wb of the non-oriented portion is too narrow, the non-aqueous electrolyte easily moves in the thickness direction of the negative electrode active material layer in the non-oriented portion. Then, the nonaqueous electrolytic solution is pushed out from the surface of the non-oriented portion to the boundary (gap) between the negative electrode active material layer and the separator facing the non-active portion, and further, the gap moves in the axial direction of the electrode body. Easier to flow out. Thereby, the internal resistance of the battery is likely to increase.
On the other hand, if the value of Wb / Wc is too large, specifically greater than 0.43, the width Wb of the non-oriented portion is too wide, so that the non-aqueous electrolyte in the non-oriented portion becomes the negative electrode active material layer. It becomes easy to move in the width direction. For this reason, the salt concentration unevenness of the non-aqueous electrolyte occurs inside the electrode body (inside the negative electrode active material layer), and the internal resistance of the battery tends to increase.

  On the other hand, in this non-aqueous electrolyte secondary battery, the value of the ratio Wb / Wc between the width Wb of the non-oriented portion and the width Wc of the negative electrode active material layer is set to 0.11 or more. Even when the layer expands, the width Wb of the non-oriented portion is not too narrow, so that the non-aqueous electrolyte moves in the thickness direction of the negative active material layer in the non-oriented portion, and the negative active material layer from the surface of the non-oriented portion. It can be suppressed that the liquid is pushed into the gap between the separator and the separator, and further, the gap moves in the axial direction of the electrode body and flows out of the electrode body. On the other hand, since the value of Wb / Wc is 0.43 or less, the width Wb of the non-oriented portion is not too wide, and the non-aqueous electrolyte moves in the width direction of the negative electrode active material layer in the non-oriented portion. It can be effectively suppressed. Therefore, in this battery, an increase in internal resistance can be more effectively suppressed.

  Furthermore, the non-aqueous electrolyte secondary battery according to any one of the above, wherein the width Wa of the orientation portion is preferably 5 ≦ Wa ≦ 10 (mm). .

If the width Wa of the alignment portion is too small, specifically less than 5 mm, it is difficult to sufficiently obtain the effect of suppressing the non-aqueous electrolyte from moving in the width direction inside the negative electrode active material layer. For this reason, salt concentration unevenness of the non-aqueous electrolyte is likely to occur inside the electrode body, and the internal resistance of the battery is likely to increase.
On the other hand, if the width Wa of the alignment portion is too large, specifically, greater than 10 mm, the non-aqueous electrolyte easily moves in the thickness direction of the negative electrode active material layer in the alignment portion. Then, the non-aqueous electrolyte is pushed out from the surface of the oriented portion to the boundary (gap) between the negative electrode active material layer and the separator, and further, this gap moves in the axial direction of the electrode body and easily flows out of the electrode body. Become. Thereby, the internal resistance of the battery is likely to increase.

  On the other hand, in this non-aqueous electrolyte secondary battery, the width Wa of the alignment portion is 5 mm or more, so that the non-aqueous electrolyte can be effectively suppressed from moving in the width direction inside the negative electrode active material layer. . On the other hand, since the width Wa of the alignment portion is 10 mm or less, the non-aqueous electrolyte moves in the thickness direction of the negative electrode active material layer in the alignment portion, and enters the gap between the negative electrode active material layer and the separator from the surface of the alignment portion. It is possible to suppress the extrusion and further the movement of the gap in the axial direction of the electrode body and the outflow to the outside of the electrode body. Therefore, in this battery, an increase in internal resistance can be more effectively suppressed.

1 is a perspective view of a lithium ion secondary battery according to an embodiment. It is the longitudinal cross-sectional view which cut | disconnected the lithium ion secondary battery which concerns on embodiment by the plane in alignment with a battery horizontal direction and a battery vertical direction. It is a perspective view of the electrode body which concerns on embodiment. It is an expanded view of an electrode body which concerns on embodiment and shows the state which mutually accumulated the positive electrode plate and the negative electrode plate through the separator. It is sectional drawing of an electrode body which concerns on embodiment and shows the state which mutually accumulated the positive electrode plate and the negative electrode plate through the separator. It is explanatory drawing which shows the process of orienting a graphite particle in the magnetic field regarding the manufacturing method of the negative electrode plate which concerns on embodiment. It is a graph which shows the relationship between the value of Wb / Wc of a negative electrode active material layer, and the resistance increase ratio of the internal resistance of a battery regarding the high-rate discharge cycle test of each battery which concerns on an Example and a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a lithium ion secondary battery (nonaqueous electrolyte secondary battery) 1 (hereinafter also simply referred to as “battery 1”) according to the present embodiment. 3 to 5 show a wound electrode body 20 constituting the battery 1. In the following description, the battery thickness direction BH, the battery lateral direction CH, and the battery vertical direction DH of the battery 1 are defined as the directions shown in FIGS. 1 and 2. The axial direction EH, the electrode body thickness direction FH, and the electrode body width direction GH along the axis AX of the electrode body 20 will be described as the directions shown in FIGS.
The battery 1 is a rectangular and sealed lithium ion secondary battery mounted on a vehicle such as a hybrid vehicle or an electric vehicle. The battery 1 includes a battery case 10, an electrode body 20 accommodated therein, a positive terminal 40 and a negative terminal 41 supported by the battery case 10, and the like. A non-aqueous electrolyte solution 17 is held in the battery case 10.

  Among these, the battery case 10 has a rectangular parallelepiped shape and is made of metal (in this embodiment, aluminum). This battery case 10 includes a rectangular parallelepiped box-shaped case main body member 11 whose upper side is opened, and a rectangular plate-shaped case lid member 13 welded in a form to close the opening 11h of the case main body member 11. . The case lid member 13 is provided with a safety valve 14 that opens when the internal pressure of the battery case 10 reaches a predetermined pressure. The case lid member 13 is formed with a liquid injection hole 13 h that communicates the inside and outside of the battery case 10 and is hermetically sealed with a sealing member 15.

  In addition, the case lid member 13 has a positive terminal 40 and a negative terminal 41 formed of an internal terminal member 43, an external terminal member 44, and a bolt 45, respectively, via an internal insulating member 47 and an external insulating member 48 made of resin. It is fixed. The positive terminal 40 is made of aluminum, and the negative terminal 41 is made of copper. In the battery case 10, the positive electrode terminal 40 is connected to the positive electrode current collector 21 m of the positive electrode plate 21 in the electrode body 20 described later, and the negative electrode terminal 41 is connected to the negative electrode current collector 31 m of the negative electrode plate 31 in the electrode body 20. Connected to.

  Next, the electrode body 20 will be described (see FIGS. 2 to 5). The electrode body 20 has a flat shape having an axis AX, the axial direction EH coincides with the battery lateral direction CH, the electrode body thickness direction FH coincides with the battery thickness direction BH, and the electrode body width direction GH extends in the battery vertical direction. The battery case 10 is housed in a form that matches the direction DH. The electrode body 20 is accommodated in the battery case 10 in a state of being surrounded by a bag-like insulating film enclosure (not shown) made of an insulating film. The electrode body 20 is obtained by compressing a belt-like positive electrode plate 21 and a belt-like negative electrode plate 31 around an axis line AX so as to overlap each other via two belt-like separators 39.

  The positive electrode plate 21 is formed by providing a positive electrode active material layer 23 in a band shape on a region extending in a part of the width direction and extending in the longitudinal direction among both main surfaces of a positive electrode current collector foil 22 made of a band-shaped aluminum foil. The positive electrode active material layer 23 includes a positive electrode active material, a conductive agent, and a binder. Also, one end of the positive electrode current collector foil 22 in the width direction is a positive electrode current collector part 21 m where the positive electrode current collector foil 22 is exposed without the positive electrode active material layer 23 in the thickness direction of the positive electrode current collector foil 22. Yes. The positive electrode terminal 40 is connected to the positive electrode current collector 21m.

The negative electrode plate 31 has a negative electrode active material layer 33, which will be described in detail later, on a region extending in the longitudinal direction JH in a part of the width direction of both main surfaces of a negative electrode current collector foil 32 made of a strip-shaped copper foil. It is provided. Also, one end in the width direction of the negative electrode current collector foil 32 is the negative electrode current collector part 31m where the negative electrode active material layer 33 is not present in the thickness direction of the negative electrode current collector foil 32 and the negative electrode current collector foil 32 is exposed. Yes. The negative electrode terminal 41 described above is connected to the negative electrode current collector 31m.
The separator 39 is a porous film made of resin, specifically, polypropylene (PP) and polyethylene (PE), and has a strip shape.

  The negative electrode active material layer 33 of this embodiment includes a negative electrode active material, a binder, and a thickener. Specifically, the negative electrode active material layer 33 is composed of graphite particles 35 as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener. : 1: 1 by weight. Of these, the graphite particles 35 are flat and have a smaller dimension in the thickness direction perpendicular to the basal plane than in the direction in which the basal plane expands.

The negative electrode active material layer 33 includes a plurality of strips (four strips in the present embodiment) extending in the longitudinal direction JH of the negative electrode plate 31 and strips extending in the longitudinal direction JH, except for the alignment portion 33a. And a plurality of non-oriented portions 33b (three in the present embodiment).
The orientation portion 33a is a portion where the X-ray diffraction intensity ratio I (110) / I (002) (orientation strength) of the graphite particles 35 is 0.04 or more (in this embodiment, 0.10). As shown schematically, the graphite particles 35 having a flat shape are oriented in a state close to the vertical direction in the thickness direction LH of the negative electrode active material layer 33.
On the other hand, the unoriented portion 33b is a portion having an X-ray diffraction intensity ratio I (110) / I (002) (orientation strength) of 0.02 or less (0.01 in this embodiment), which is schematically shown in FIG. As shown in FIG. 5, the graphite particles 35 having a flat shape are arranged in a state in which the main surface of the negative electrode current collector foil 32 is close to the lateral direction in the spreading direction (left and right direction in FIG. 5). In the negative electrode active material layer 33 in FIG. 5, the binder (SBR) and the thickener (CMC) are not shown.

Each orientation portion 33a has a width Wa within a range of 5 ≦ Wa ≦ 10 (mm), and in this embodiment, the width Wa = 5 mm. These alignment portions 33a are formed at equal intervals. Of the four alignment portions 33a, the two alignment portions 33a are respectively formed at both end portions 33t in the width direction KH of the negative electrode active material layer 33. ing. The remaining two alignment portions 33 a are formed in the inner portion 33 g on the inner side in the width direction KH than both end portions 33 t of the negative electrode active material layer 33.
On the other hand, each unoriented portion 33b has a width Wb of Wb = 28 mm. Since the entire width Wc of the negative electrode active material layer 33 is Wc = 105 mm, Wb / Wc = 0.27, which satisfies 0.11 ≦ Wb / Wc ≦ 0.43. These unoriented portions 33 b are all formed in the inner portion 33 g of the negative electrode active material layer 33.

  Here, the manufacturing method of this negative electrode plate 31 is demonstrated. In advance, the negative electrode active material (graphite particles 35), the binder (SBR), and the thickener (CMC) are weighed so that the weight ratio is 98: 1: 1, and these are added to the dispersion medium (water). And mix to prepare the negative electrode paste. Next, a negative electrode current collector foil 32 is prepared, and the negative electrode paste is applied to both main surfaces thereof to form a negative electrode plate 31 ′ having an undried negative electrode active material layer 33 ′ on the negative electrode current collector foil 32. (See FIG. 6).

  Next, in the undried negative electrode active material layer 33 ′, in a direction (vertical direction, thickness direction LH in FIG. 6) orthogonal to the main surface of the negative electrode current collector foil 32, the portion that becomes the orientation portion 33 a after drying. A magnetic field generated by magnetic lines of force is applied to orient the graphite particles 35 contained in the negative electrode active material layer 33 ′ in a state close to the vertical direction. Specifically, as shown in FIG. 6, a negative electrode plate 31 ′ on which an undried negative electrode active material layer 33 ′ is formed is conveyed between a pair of magnets MG <b> 1 and MG <b> 2 that are arranged to face each other. A magnetic field that generates magnetic lines of force in the thickness direction LH is applied to a portion of the active material layer 33 ′ that becomes the orientation portion 33a after drying.

  Thereby, in the undried negative electrode active material layer 33 ′, the graphite particles 35 included in the portion corresponding to the orientation portion 33a are oriented in a state in which the spreading direction of the basal surface is close to the vertical direction parallel to the thickness direction LH. . And in the negative electrode plate 31 after manufacture, the orientation intensity | strength of the orientation part 33a will be 0.10 as mentioned above. On the other hand, in the undried negative electrode active material layer 33 ′, the magnetic field is hardly applied to the graphite particles 35 included in the portion corresponding to the unoriented portion 33 b. For this reason, the spreading direction of the basal surface is almost parallel to the main surface of the negative electrode current collector foil 32 and remains in a lateral direction. Therefore, in the negative electrode plate 31 after manufacture, the orientation strength of the unoriented portion 33b is 0.01 as described above.

  Next, the negative electrode active material layer 33 ′ of the negative electrode plate 31 ′ is dried. Thereafter, the negative electrode plate 31 'is compressed to a predetermined thickness by a roll press. Thus, the negative electrode plate 31 in which the negative electrode active material layer 33 has the oriented portion 33a and the non-oriented portion 33b is formed.

(Examples and Comparative Examples)
Subsequently, the result of the test conducted in order to verify the effect of this invention is demonstrated. First, as Examples 1 to 6, while the width Wa (= 5 mm) and the orientation strength (= about 0.1) of the orientation part of the negative electrode active material layer are set to constant values, the number of orientation parts is 8 to 3 Six types of batteries changed to strips were prepared.
Moreover, as Examples 7-10, the width | variety Wa (= 10mm) and orientation intensity | strength (= about 0.1) of the orientation part of a negative electrode active material layer are made into a constant value, and the number of orientation parts is 6-3. Four types of batteries that were changed to strips were prepared.
Further, as Examples 11 to 15, the width of the alignment portion Wa (= 5 mm) and the alignment strength (= 0.05) of the negative electrode active material layer were set to constant values, and the number of alignment portions was 7 to 3 Five types of batteries were prepared.
In each of the batteries of Examples 1 to 15, the width Wb and the number of strips of the non-oriented portion are changed in accordance with the change of the number of oriented portions as described above.

On the other hand, as Comparative Example 1, a battery in which no orientation part was provided in the negative electrode active material layer (the whole negative electrode active material layer was an unoriented part) was prepared.
Further, as Comparative Examples 2 and 3, the alignment strength was 0.10, and the alignment portions were provided only at both end portions in the width direction KH of the negative electrode active material layer (the alignment portions on the inner side of the negative electrode active material layer in the width direction KH). A battery was prepared. In Comparative Example 2, the width Wa of the orientation part was 5 mm, and in Comparative Example 3, the width Wa of the orientation part was 10 mm.
In addition, about each battery of Examples 1-15 and Comparative Examples 1-3, the part other than the above was made the same as the battery 1 of Embodiment 1.

  Next, for each of the batteries of Examples 1 to 15 and Comparative Examples 1 to 3, an “input characteristic test” was performed to determine the 10-second input power (W) of the battery. Specifically, in a temperature environment of 25 ° C., after each battery is adjusted to SOC 60%, until the battery voltage becomes 4.1 V with power A (W), power B (W), and power C (W) Charging time X (second), charging time Y (second), and charging time Z (second) when input were measured. Then, from these data, a graph with power (W) on the horizontal axis and charging time (seconds) on the vertical axis is drawn, and the power when the charging time is 10 seconds is obtained from this graph, and this is calculated for 10 seconds. Input power (W) was used. Table 1 shows the 10-second input power ratio (%) of each battery when the 10-second input power of the battery of Comparative Example 1 is used as a reference (100%). The results are shown in Table 1.

  As is apparent from Table 1, each of the batteries of Examples 1 to 15 and Comparative Examples 2 and 3 (batteries other than the battery of Comparative Example 1) provided with an orientation portion in the negative electrode active material layer has an input power of 10 seconds. The ratio exceeds 100%, which indicates that the input characteristics are superior to the battery of Comparative Example 1. Further, it can be seen that the larger the total width of the alignment portion (= width Wa × number of stripes), the higher the input power ratio for 10 seconds and the better the input characteristics. In addition, when the total width of the alignment portions is the same (for example, Example 2 and Example 11, Example 3, Example 10, and Example 12), the higher the alignment strength, the higher the input power ratio for 10 seconds. It can be seen that the input characteristics are excellent.

  The reason is considered as follows. That is, in the orientation part of the negative electrode active material layer, the flat graphite particles are arranged in a state close to the vertical direction, and the higher the orientation strength, the more the graphite particles are arranged in a state close to the vertical direction. Therefore, lithium is more easily inserted into the graphite particles from the edge surface during charging in the oriented portion than in the unoriented portion, and in the oriented portion having higher orientation strength. Therefore, it is considered that the input characteristics are improved by providing the alignment portion in the negative electrode active material layer, and the input characteristics are further improved by further increasing the total width of the alignment portions or increasing the alignment strength of the alignment portions. .

  Next, for each of the batteries of Examples 1 to 15 and Comparative Examples 1 to 3, a “high rate discharge cycle test” in which high-rate and short-time discharge and low-rate and long-time charge are repeatedly performed is performed. The resistance increase rate (%) of the resistance was determined. Specifically, in a temperature environment of 25 ° C., each battery was adjusted to 100% SOC, discharged at a constant current of 20 C for 30 seconds, and then rested for 30 minutes. Thereafter, the battery was charged with a constant current of 2C for 300 seconds and then rested for 30 minutes. This charging / discharging was made into 1 cycle, and this was performed 2000 cycles.

Then, in a temperature environment of 25 ° C., each battery was adjusted to 60% SOC, and then discharged for 10 seconds at a constant current of 20 C. The battery voltage before discharge, the battery voltage after discharge for 10 seconds, and 20 C The internal resistance (IV resistance) of each battery was determined from the corresponding current value. Moreover, about each battery, the ratio of the internal resistance after the test with respect to the internal resistance before the test was calculated | required, and it was set as the resistance increase rate of each battery. Furthermore, the resistance increase ratio (%) of each battery when the resistance increase rate of the battery of Comparative Example 1 was used as a reference (100%) was determined. The results are shown in Table 1 and FIG.
In addition, in FIG. 7, the result of each battery which concerns on Examples 1-6 and the comparative example 2 was shown by the "♦" mark, and the graph was drawn with the continuous line. Moreover, the result of each battery according to Examples 7 to 10 and Comparative Example 3 is indicated by “「 ”, and a graph is drawn with a one-dot chain line. Moreover, the result of each battery according to Examples 11 to 15 is indicated by “▲”, and a graph is drawn with a two-dot chain line. In addition, since the comparative example 1 which is a reference | standard (100%) does not have an orientation part, it is not described in the graph of FIG.

  As is clear from Table 1 and FIG. 7, in each battery of Comparative Examples 2 and 3 in which the orientation portions are provided only at both ends in the width direction KH of the negative electrode active material layer, the resistance increase ratio is 99% or 101%. It can be seen that the increase in internal resistance is comparable to that of the battery of Comparative Example 1 in which the orientation portion was not provided in the negative electrode active material layer. On the other hand, in each battery of Examples 1-15 in which a plurality of alignment portions were provided in the negative electrode active material layer, and at least one of the alignment portions was provided on the inner side in the width direction KH of the negative electrode active material layer, The increase ratio is 69 to 91%, which indicates that the increase in internal resistance is suppressed as compared with the batteries of Comparative Examples 1 to 3.

  The reason is considered as follows. That is, in the orientation portion, the flat graphite particles 35 are oriented in a state close to the vertical direction. For this reason, the non-aqueous electrolyte solution 17 is less likely to move in the width direction KH of the negative electrode active material layer in the oriented portion than in the non-oriented portion. The non-aqueous electrolyte solution 17 in the negative electrode active material layer is formed on the inner side of the negative electrode active material layer by forming a plurality of the alignment portions and forming at least one stripe on the inner side in the width direction KH of the negative electrode active material layer. It becomes difficult to move the part in the width direction KH. Accordingly, it is possible to suppress the occurrence of non-uniform salt concentration of the non-aqueous electrolyte 17 inside the electrode body (inside the negative electrode active material layer), and to suppress the increase in the internal resistance of the battery due to the non-uniform salt concentration. Conceivable.

  Further, as apparent from Table 1 and FIG. 7, when the ratio Wb / Wc ratio between the width Wb of the unoriented portion and the width Wc of the negative electrode active material layer is smaller than 0.11, the resistance increase ratio is about 80. Higher than%. On the other hand, when Wb / Wc ≧ 0.11, the resistance increase ratio becomes lower than about 80%, and it can be seen that the increase in internal resistance can be effectively suppressed. This is also true for each of the batteries according to Examples 1 to 6 in which the width Wa of the orientation portion was 5 mm (graphs indicated by ♦ and solid lines), and Examples 7 to 10 in which the width Wa of the orientation portion was 10 mm. The same applies to each battery according to the above (graphs indicated by ▲ and one-dot chain lines).

  The reason is considered as follows. That is, when Wb / Wc <0.11, when the negative electrode active material layer expands during charging, the width Wb of the non-oriented portion is too narrow. It becomes easy to move in the thickness direction LH of the layer. Then, the non-aqueous electrolyte solution 17 is pushed out from the surface of the non-oriented portion to the boundary (gap) between the negative electrode active material layer and the separator 39, and further moves in the gap in the axial direction EH of the electrode body. It becomes easy to flow out. Thereby, it is considered that the internal resistance of the battery is likely to increase. Therefore, it is preferable that Wb / Wc ≧ 0.11.

On the other hand, even if the value of Wb / Wc is larger than 0.43, the resistance increase ratio becomes high (greater than about 80%). Conversely, it can be seen that when Wb / Wc ≦ 0.43, the resistance increase ratio can be effectively reduced (the resistance increase ratio can be reduced to about 80% or less), and the increase in internal resistance can be effectively suppressed. This is also true for each of the batteries according to Examples 1 to 6 and Comparative Example 2 in which the width Wa of the oriented portion was 5 mm (graphs indicated by the ♦ and solid lines), and the width Wa of the oriented portion was 10 mm. The same applies to each of the batteries 10 to 10 and Comparative Example 3 (graphs indicated by ▲ and one-dot chain lines).
The reason is that if Wb / Wc> 0.43, the width Wb of the non-oriented portion is too wide, so that the non-aqueous electrolyte 17 easily moves in the width direction KH of the negative electrode active material layer in the non-oriented portion. . For this reason, it is considered that the salt concentration unevenness of the non-aqueous electrolyte solution 17 occurs inside the electrode body (inside the negative electrode active material layer), and the internal resistance of the battery tends to increase. Therefore, it is preferable that Wb / Wc ≦ 0.43.

Further, as is clear from Table 1 and FIG. 7, each battery of Examples 11 to 15 (orientation strength = about 0.1) with the orientation strength = 0.05 When comparing each of the batteries according to Examples 2 to 6 corresponding to Examples 11 to 15 (graphs indicated by ◆ and solid lines), each of the batteries according to Examples 2 to 6 having higher orientation strength was obtained. However, the resistance increase ratio can be lowered. Therefore, it can be seen that an increase in internal resistance can be effectively suppressed.
The reason is that when the orientation strength is increased, that is, when the graphite particles 35 in the orientation portion are oriented in a state closer to the longitudinal direction, the non-aqueous electrolyte solution 17 has a width of the negative electrode active material layer in the orientation portion. It is possible to effectively suppress movement in the direction KH. For this reason, it is considered that the internal resistance of the battery is difficult to increase. Therefore, it is preferable to increase the value of the orientation strength.

  As described above, in the lithium ion secondary battery 1 of the present embodiment, the negative electrode active material layer 33 has the X-ray diffraction intensity ratio I (110) / I (002) of the graphite particles 35 of 0.04 or more. A certain orientation portion 33a is provided. In this orientation part 33a, the graphite particle 35 which makes flat shape is orientated in the state close | similar to the vertical direction. For this reason, the non-aqueous electrolyte solution 17 is less likely to move in the width direction KH of the negative electrode active material layer 33 in the oriented portion 33a than in the unoriented portion 33b.

  The alignment portion 33a is formed in a plurality of strips (four strips in the present embodiment (Example 5)) in a strip shape extending in the longitudinal direction JH of the negative electrode plate 31, and at least one strip of the alignment portions 33a (this implementation). In the embodiment (Example 5), 2) is formed on the inner side 33g of the negative electrode active material layer 33 in the width direction KH. This makes it difficult for the nonaqueous electrolytic solution 17 in the negative electrode active material layer 33 to move in the width direction KH through the inner portion 33g of the negative electrode active material layer 33. Therefore, when the above-described high-rate discharge cycle test is performed, the non-aqueous electrolyte solution 17 in the negative electrode active material layer 33 moves in the negative electrode active material layer 33 in the width direction KH, and the inside of the electrode body 20 (negative electrode It is possible to suppress the occurrence of non-uniform salt concentration of the nonaqueous electrolytic solution 17 in the active material layer 33). And it can suppress that the internal resistance of the battery 1 increases due to this salt concentration nonuniformity.

Furthermore, in the present embodiment, since both end portions 33t in the width direction KH of the negative electrode active material layer 33 are the alignment portions 33a, the nonaqueous electrolytic solution 17 held in the negative electrode active material layer 33 is converted into the negative electrode active material layer. 33 hardly flows out of the negative electrode active material layer 33 from both end faces in the width direction KH. Therefore, an increase in internal resistance when a high rate discharge cycle test is performed can be more effectively suppressed.
Further, in the present embodiment, since the plurality of alignment portions 33 a are arranged at regular intervals, the alignment portions 33 a are arranged on the negative electrode active material layer 33 in a well-balanced manner. For this reason, it can suppress more effectively that the salt concentration nonuniformity of the non-aqueous electrolyte 17 arises inside the electrode body 20 (inside of the negative electrode active material layer 33), and it is further effective that the internal resistance of the battery 1 increases. Can be suppressed.

  In the present embodiment, since the value of the ratio Wb / Wc between the width Wb of the unoriented portion 33b and the width Wc of the negative electrode active material layer is 0.11 or more, the negative electrode active material layer 33 expands during charging. However, since the width Wb of the non-oriented portion 33b is not too narrow, the non-aqueous electrolyte solution 17 moves in the thickness direction LH of the negative electrode active material layer 33 in the non-oriented portion 33b, and the negative electrode active material 33 is moved from the surface of the non-oriented portion 33b. It is possible to prevent the material layer 33 and the separator 39 from being pushed out to the boundary (gap), and further moving through the gap in the axial direction EH of the electrode body 20 and flowing out of the electrode body 20. On the other hand, since the value of Wb / Wc is 0.43 or less, the width Wb of the non-oriented portion 33b is not too wide, and the non-aqueous electrolyte 17 is in the width direction of the negative electrode active material layer 33 in the non-oriented portion 33b. The movement to KH can be effectively suppressed. Therefore, in this battery 1, it is possible to more effectively suppress the increase in internal resistance.

  Moreover, in this embodiment, since the width Wa of the orientation part 33a is 5 mm or more, it can suppress effectively that the non-aqueous electrolyte 17 moves to the width direction KH inside the negative electrode active material layer 33. FIG. On the other hand, since the width Wa of the alignment portion 33a is 10 mm or less, the nonaqueous electrolytic solution 17 moves in the thickness direction LH of the negative electrode active material layer 33 in the alignment portion 33a, and the negative electrode active material from the surface of the alignment portion 33a. It is possible to suppress the extrusion to the boundary (gap) between the layer 33 and the separator 39, and further the movement of the gap in the axial direction EH of the electrode body 20 to flow out of the electrode body 20. Therefore, in this battery 1, it is possible to more effectively suppress the increase in internal resistance.

  In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

1 Lithium ion secondary battery (non-aqueous electrolyte secondary battery)
DESCRIPTION OF SYMBOLS 10 Battery case 17 Non-aqueous electrolyte 20 Electrode body 21 Positive electrode plate 31 Negative electrode plate 32 Negative electrode current collection foil 33 Negative electrode active material layer 33a Orientation part 33b Unorientation part 33t End part 33g Inner part 35 Graphite particle 39 Separator 40 Positive electrode terminal 41 Negative electrode Terminal EH Axis direction JH (Negative electrode plate) Longitudinal direction KH (Negative electrode active material layer) Width direction LH (Negative electrode active material layer) Thickness direction

Claims (1)

A non-aqueous electrolyte secondary battery comprising a wound electrode body formed by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate through a strip-shaped separator,
The negative electrode plate is
A strip-like shape extending in the longitudinal direction of the negative electrode plate, and having a negative electrode active material layer containing flat graphite particles whose dimensions in the direction perpendicular to the basal surface are smaller than the spreading direction of the basal surface,
The negative electrode active material layer is
A strip extending in the longitudinal direction, and a plurality of alignment portions having an X-ray diffraction intensity ratio I (110) / I (002) of the graphite particles of 0.04 or more, wherein at least one of the alignment portions Is a plurality of alignment portions formed on the inner side of the inner side of the both ends of the negative electrode active material layer in the width direction;
A non-aqueous electrolyte secondary battery having the X-ray diffraction intensity ratio I (110) / I (002) of 0.02 or less and a plurality of unoriented portions forming portions other than the oriented portions.

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