JP2009289703A - Lithium ion battery, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress decrease in concentration of lithium ions used for charge and discharge. <P>SOLUTION: A lithium ion battery (1) includes: a power generation element (11) having a positive electrode element (12), and a negative electrode element (13), and containing a first electrolyte; a case (10) for housing the power generation element; and a second electrolyte (20) housed in the case and positioned on the outside of the power generation element. The concentration of lithium ions in the second electrolyte is made higher than that of lithium ions in the first electrolyte. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lithium ion battery and a method for producing the same, and more specifically, lithium capable of suppressing a decrease in the concentration of lithium ions contained in an electrolytic solution during charge / discharge. The present invention relates to an ion battery or the like.

  FIG. 5 shows a configuration of a lithium ion battery (unit cell). Here, a separator 103 containing an electrolytic solution is disposed between the positive electrode element 101 and the negative electrode element 102. The positive electrode element 101 includes a current collector plate 101a and a positive electrode layer 101b formed on the surface of the current collector plate 101a and containing an active material corresponding to the positive electrode. The negative electrode element 102 includes a current collector plate 102a and a negative electrode layer 102b formed on the surface of the current collector plate 102a and containing an active material corresponding to the negative electrode. Note that in FIG. 5, the positive electrode element 101 and the negative electrode element 102 are shown apart from the separator 103, but actually, the positive electrode layer 101 b and the negative electrode layer 102 b are in contact with the separator 103.

  In the configuration of the lithium ion battery shown in FIG. 5, when charging, lithium ions move from the positive electrode layer 101b toward the negative electrode layer 102b, and when discharging, lithium ions move from the negative electrode layer 102b toward the positive electrode layer 101b. Moving. FIG. 5 shows the movement of lithium ions during discharge.

On the other hand, when a battery module (assembled battery) is configured by arranging a plurality of lithium ion batteries in parallel, a force (external force) F for holding the battery module acts on both ends of the battery module. I am letting. In this case, as shown in FIG. 5, an external force F acts on one lithium ion battery.
Japanese Patent Laid-Open No. 10-50339

  As shown in FIG. 5, when discharging is performed in a state where an external force F is applied to the lithium ion battery, the volume of the negative electrode layer 102b decreases due to the separation of lithium ions from the negative electrode layer 102b. . That is, the negative electrode layer 102b contracts in the direction in which the external force F acts by receiving the external force F.

  And when the negative electrode layer 102b shrinks, the electrolyte solution which exists in the surface or inside of the negative electrode layer 102b may move to the outside of the negative electrode layer 102b together with lithium ions. Specifically, the electrolytic solution may move in the direction indicated by arrow D in FIG. Here, FIG. 6 is a front view when the negative electrode layer 102b is viewed from the direction in which the external force F acts.

  As described above, if the electrolyte moves to the outside of the negative electrode layer 102b together with lithium ions, the concentration of lithium ions used for charging / discharging may decrease, and the output performance of the lithium ion battery may decrease. There is.

  Then, the objective of this invention is providing the lithium ion battery which can suppress that the density | concentration of the lithium ion used for charging / discharging falls.

  A lithium ion battery according to the first invention of the present application includes a positive electrode element and a negative electrode element, and includes a power generation element including a first electrolyte, a case for storing the power generation element, a case accommodated in the case, And a second electrolyte solution positioned. The lithium ion concentration in the second electrolytic solution is higher than the lithium ion concentration in the first electrolytic solution.

  Here, the negative electrode element is formed on the current collector plate and has a negative electrode layer containing an active material. When the negative electrode layer is deformed during discharge, the first electrolyte moves to the outside of the power generation element. . And a negative electrode layer deform | transforms by receiving the external force for pinching a lithium ion battery.

  Further, the concentration of lithium ions in the second electrolytic solution can be made substantially equal to the concentration of lithium ions in the first electrolytic solution that moves to the outside of the power generation element by deformation of the negative electrode layer. Thereby, due to deformation of the negative electrode layer during discharge, even if the first electrolyte containing lithium ions moves outside the power generation element and mixes with the second electrolyte, the concentration of lithium ions changes. Can be prevented.

  A second invention of the present application is a method for manufacturing a lithium ion battery in which a power generation element including a positive electrode element and a negative electrode element is housed in a case together with an electrolyte, and by injecting the first electrolyte in the case A first step of including the first electrolyte in the power generation element, and a second electrolyte having a higher concentration of lithium ions than the concentration of lithium ions in the first electrolyte is injected into the case. 2 steps.

  Here, in the first step, the first electrolytic solution located outside the power generation element is discharged out of the case, and in the second step, the second electrolytic solution in an amount corresponding to the discharged amount of the first electrolytic solution. Can be injected into the case. Thereby, the 2nd electrolyte solution can be located in the space inside a case in the exterior of an electric power generation element.

  In addition, the negative electrode element is formed on the current collector plate and has a negative electrode layer containing an active material, and the first electrolyte moves to the outside of the power generation element by deformation of the negative electrode layer during discharge. The concentration of lithium ions in the electrolyte solution can be made substantially equal. Thereby, due to deformation of the negative electrode layer during discharge, even if the first electrolyte containing lithium ions moves outside the power generation element and mixes with the second electrolyte, the concentration of lithium ions changes. Can be prevented.

  In the present invention, the concentration of lithium ions in the second electrolyte solution located outside the power generation element is higher than the concentration of lithium ions in the first electrolyte solution located inside the power generation element. As a result, even when the first electrolyte moves to the outside of the power generation element together with lithium ions during discharge, the second electrolyte moves to the inside of the power generation element, and the concentration of lithium ions in the power generation element decreases. Can be suppressed.

  Examples of the present invention will be described below.

  First, the structure of the lithium ion battery which is Example 1 of the present invention will be described.

  FIG. 1 is a cross-sectional view showing the internal configuration of the lithium ion battery of this example. Here, the X axis, the Y axis, and the Z axis shown in FIG. 1 are axes orthogonal to each other. And the Z-axis has shown the direction where gravity acts.

  The lithium ion battery 1 includes a battery case 10 and a power generation element 11 accommodated inside the battery case 10. The power generation element 11 is an element that can be charged and discharged, and is housed in a wound state inside the battery case 10 as shown in FIG. Here, FIG. 2 is a cross-sectional view of the lithium ion battery 1 taken along the XZ plane.

  As shown in FIG. 3, the power generation element 11 includes a positive electrode element 12, a negative electrode element 13, and a separator 14 that is disposed between the positive electrode element 12 and the negative electrode element 13 and contains an electrolytic solution. The separator 14 is a member that can hold an electrolytic solution, and for example, a nonwoven fabric can be used.

  Here, the positive electrode element 12 includes a current collecting plate 12a and a positive electrode layer 12b formed on the surface of the current collecting plate 12a, as in the configuration shown in FIG. The positive electrode layer 12b is formed on the surface of the current collector plate 12a facing the separator 14. The positive electrode layer 12b can also be formed on both surfaces of the current collector plate 12a.

  The positive electrode layer 12b is a layer containing an active material corresponding to the positive electrode. As the active material of the positive electrode layer 12b, for example, a lithium-transition metal composite oxide can be used. In addition to the active material, the positive electrode layer 12b can contain a conductive agent or the like. As the conductive agent, for example, acetylene black, carbon black, graphite, carbon fiber, or carbon nanotube can be used.

  Similarly to the configuration shown in FIG. 5, the negative electrode element 13 has a current collector plate 13a and a negative electrode layer 13b formed on the surface of the current collector plate 13a. The negative electrode layer 13b is formed on the surface of the current collector plate 13a that faces the separator 14. The negative electrode layer 13b can also be formed on both surfaces of the current collector plate 13a. The negative electrode layer 13b is a layer containing an active material corresponding to the negative electrode. As the active material of the negative electrode layer, for example, carbon can be used. In addition to the active material, the negative electrode layer 13b can contain a conductive agent or the like.

  An electrode in which the positive electrode layer 12b is formed on one surface of the current collector and the negative electrode layer 13b is formed on the other surface of the current collector can also be used. This electrode is a so-called bipolar electrode. In this embodiment, as shown in FIGS. 1 and 2, the lithium ion battery 1 has a so-called square configuration, but is not limited thereto, and may be a so-called cylindrical configuration. That is, the battery case 10 may be rectangular or cylindrical, and the power generation element 11 may be housed in the battery case 10 while being wound.

  On the other hand, as shown in FIG. 1, an electrolytic solution 20 as an excess liquid is accommodated in the battery case 10. The electrolyte 20 is located outside the power generation element 11 in the battery case 10 and is in contact with the power generation element 11. The electrolytic solution 20 is used to ensure the charge / discharge performance of the power generation element 11. Here, an electrolyte solution different from the electrolyte solution 20 is contained inside the power generation element 11 as described later.

  In addition, the quantity of the electrolyte solution 20 can be set suitably. Moreover, gas exists in the area | region where the electrolyte solution 20 is not located among the spaces in the battery case 10. Examples of this gas include air and rare gases such as argon.

  In FIG. 1, a positive electrode terminal 21 is electrically and mechanically connected to the positive electrode tab 12c connected to the current collector plate 12a of the positive electrode element 12. Here, as shown in FIG. 1, the positive electrode tab 12 c connected to the positive electrode terminal 21 protrudes from one end portion in the Y direction of the power generation element 11 in a wound state. The positive electrode tab 12c can be configured integrally with the current collector plate 12a of the positive electrode element 12, or can be configured as a separate body.

  The negative electrode terminal 22 is electrically and mechanically connected to the negative electrode tab 13 c connected to the current collector plate 13 a of the negative electrode element 13. Here, the negative electrode tab 13c connected to the negative electrode terminal 22 protrudes from the other end portion in the Y direction of the power generation element 11 in the wound state. The negative electrode tab 13c can be configured integrally with the current collector plate 13a of the negative electrode element 13, or can be configured as a separate body.

  The positive electrode terminal 21 and the negative electrode terminal 22 protrude from the upper surface of the battery case 10 and are electrically connected to an electronic device (not shown) via wiring (not shown). Thereby, an electronic device can be driven using the output of the lithium ion battery 1.

  Here, when the lithium ion battery 1 is used as a vehicle drive source, a plurality of lithium ion batteries 1 are prepared, and these lithium ion batteries 1 are electrically connected in series, whereby a battery module (assembly) Battery). And energy required for driving | running | working of a vehicle from a battery module can be taken out, and the kinetic energy generated at the time of braking of a vehicle can be stored in a battery module as regenerative electric power.

  In addition, the positive electrode terminal 21 and the negative electrode terminal 22 in each lithium ion battery 1 are electrically connected to the positive electrode terminal 21 and the negative electrode terminal 22 in the other lithium ion batteries 1 via bus bars. Further, examples of the vehicle including the battery module include a hybrid vehicle used together with another power source such as an internal combustion engine or a fuel cell, and an electric vehicle including only the battery module as a power source. Examples of devices that are electrically connected to the battery module include an inverter for driving a vehicle driving motor and a DC / DC converter for converting the output (voltage value) of the battery module.

  Next, the manufacturing process of the lithium ion battery 1 will be described.

  First, the positive electrode element 12 and the negative electrode element 13 are respectively manufactured, and the positive electrode element 12 and the negative electrode element 13 are laminated with the separator 14 interposed therebetween as shown in FIG. Here, the positive electrode element 12 is obtained by applying a material constituting the positive electrode layer 12b to the current collector plate 12a. Moreover, the negative electrode element 13 is obtained by apply | coating the material which comprises the negative electrode layer 13b with respect to the current collecting plate 13a. In addition, the material which comprises the positive electrode layer 12b and the negative electrode layer 13b can be apply | coated using the coating device which used the gravure roll or the spray, for example.

  Next, the power generation element 11 in which the positive electrode element 12, the negative electrode element 13, and the separator 14 are laminated is wound as shown in FIG. Then, the wound power generation element 11 is accommodated in the battery case 10, and the electrolytic solution is injected into the battery case 10. As an electrolytic solution injected into the battery case 10, an electrolytic solution (first electrolytic solution) included in the power generation element 11 and an electrolytic solution (second electrolytic solution) as a surplus liquid located outside the power generation element 11 are used. Liquid).

  Here, the step of injecting the electrolyte into the battery case 10 will be described with reference to FIG.

  After the inside of the battery case 10 is in a reduced pressure state in step S10, the first electrolyte is injected into the battery case 10 in step S11. In the first electrolytic solution, the lithium ion concentration is set to a predetermined value. The predetermined value is a lithium ion concentration set in advance based on the characteristics of the lithium ion battery 1, and can be set to, for example, 1.0 [mol / L]. The first electrolytic solution is different from the above-described electrolytic solution 20 with respect to the concentration of lithium ions.

  The first electrolytic solution penetrates into the power generation element 11 by injecting the first electrolytic solution after the inside of the battery case 10 is in a reduced pressure state. Specifically, the first electrolytic solution penetrates into the separator 14, the positive electrode layer 12b and the negative electrode layer 13b, and the gap between the separator 14 and the positive electrode layer 12b (and the negative electrode layer 13b).

  Next, after the inside of the battery case 10 is in a reduced pressure state in step S12, the first electrolytic solution is injected into the battery case 10 in step S13. This first electrolytic solution is the same as the first electrolytic solution used in step S11. The first electrolytic solution can be infiltrated into the power generation element 11 also by the processing in steps S12 and S13.

  In the present embodiment, the first electrolytic solution is injected in two times into the battery case 10 in a decompressed state. Thereby, the first electrolytic solution can efficiently penetrate into the power generation element 11. In addition, the frequency | count of inject | pouring a 1st electrolyte solution is not restricted to 2 times, It can set suitably. And it can suppress that the quantity of 1st electrolyte solution varies in the inside of the electric power generation element 11 by performing injection | pouring process of 1st electrolyte solution in multiple times.

  Here, in the processing up to step S13, the amount (volume) of the first electrolytic solution injected into the battery case 10 is set in advance.

  When the injection process in step S13 is completed, the first electrolytic solution as the surplus liquid is present in the space located outside the power generation element 11 among the spaces in the battery case 10.

  Next, in step S <b> 14, the first electrolytic solution as an excess liquid existing inside the battery case 10 is discharged to the outside of the battery case 10, and the amount (volume) of the discharged first electrolytic solution is measured. . Here, even if the first electrolytic solution as the surplus liquid is discharged to the outside of the battery case 10, the first electrolytic solution remains inside the power generation element 11. That is, the electrolytic solution used for charging / discharging the power generation element 11 is the first electrolytic solution used in the injection processing in steps S11 and S13.

  In the present embodiment, the amount of the first electrolyte discharged to the outside of the battery case 10 is directly measured, but the present invention is not limited to this. That is, the amount of the first electrolyte discharged outside the battery case 10 can be indirectly measured.

  Specifically, the weight of the battery case 10 at the time when the injection process of step S13 is completed is measured, and the weight of the battery case 10 after the first electrolytic solution is discharged is measured. The weight of the battery case 10 here includes not the weight of the battery case 10 itself but the weight of the power generation element 11 and the first electrolytic solution housed in the battery case 10. Then, by obtaining the difference in the weight of the battery case 10, the amount of the first electrolytic solution discharged to the outside of the battery case 10 can be specified.

  Next, after the inside of the battery case 10 is in a reduced pressure state in step S15, the second electrolyte is injected into the battery case 10 in step S16. The amount (volume) of the second electrolytic solution is substantially equal to the amount (volume) of the first electrolytic solution measured in step S14. Further, the concentration of lithium ions in the second electrolytic solution is higher than the concentration of lithium ions in the first electrolytic solution. The second electrolytic solution injected into the battery case 10 becomes the electrolytic solution 20 as the surplus liquid described above.

  Here, the concentration of lithium ions in the second electrolytic solution can be set as described below.

  First, by receiving an external force F (see FIG. 5), the concentration of lithium ions in the electrolytic solution leaking from the inside of the power generation element 11 to the outside is measured. Specifically, the lithium ion concentration in the electrolytic solution leaking outside the power generation element 11 is measured by receiving the external force F in a state where the power generation element 11 is continuously discharged. And the density | concentration of the lithium ion in a 2nd electrolyte solution is set so that it may become substantially equal to the density | concentration of the measured lithium ion.

  In step S17, the inlet used to inject the first and second electrolytes is closed. Here, the process of closing the injection port is to temporarily close the injection port because the injection port may be opened again as described later. The process of injecting the electrolytic solution into the battery case 10 is completed by the processing described above.

  Here, after the process shown in FIG. 4 is completed, the power generation element 11 is charged and discharged. At this time, since gas may be generated from the power generation element 11, the closed inlet is returned to the open state, and the gas present in the battery case 10 is discharged to the outside. Thereafter, for example, the lithium ion battery 1 is obtained by closing the inlet by welding. Here, in order to prevent the electrolyte in the battery case 10 from leaking to the outside of the battery case 10 through the inlet, the inlet needs to be completely closed.

  According to the present embodiment, as described above, the lithium ion battery 1 in the present embodiment can be obtained only by changing the step of injecting the electrolytic solution.

  In the present embodiment, the electrolytic solution is injected after the inside of the battery case 10 is in a reduced pressure state, but the present invention is not limited to this. For example, the electrolytic solution can be injected using gravity, or the electrolytic solution can be injected using centrifugal force.

  As described with reference to FIGS. 5 and 6, due to the deformation of the negative electrode layer 13 b during discharge, the first electrolyte present inside or on the surface of the negative electrode layer 13 b leaks to the outside of the power generation element 11 together with lithium ions. May end up. Here, when the lithium ion battery 1 is continuously discharged, in the first electrolyte solution located in the surface layer portion of the negative electrode layer 13b, the concentration of lithium ions is primarily increased. That is, at the time of discharging, lithium ions move from the negative electrode layer 13b toward the positive electrode layer 12b, so that a large amount of lithium ions exist in the surface layer portion of the negative electrode layer 13b.

  At this time, if the first electrolyte located in the surface layer portion of the negative electrode layer 13b leaks outside the power generation element 11, more lithium ions leak outside the power generation element 11 together with the first electrolyte. It will end up.

  The first electrolytic solution leaking from the power generation element 11 is mixed with the electrolytic solution (second electrolytic solution) 20 as an excess liquid located outside the power generation element 11. In general, since the amount of the first electrolytic solution leaking from the power generation element 11 is smaller than the amount of the electrolytic solution 20, the concentration of lithium ions in the electrolytic solution 20 hardly changes.

  Here, in the conventional lithium ion battery, an electrolytic solution having a constant lithium ion concentration is used as the electrolytic solution injected into the battery case. In addition, the lithium ion concentration in the electrolyte solution leaking from the power generation element may be higher than the lithium ion concentration in the electrolyte solution located outside the power generation element. In this case, the electrolyte solution leaking from the power generation element is mixed with the electrolyte solution located outside the power generation element, so that the concentration of lithium ions is diluted.

  The electrolyte that leaks from the power generation element and mixes with the electrolyte may return to the inside of the power generation element when the power generation element is charged or left to stand. At this time, the lithium ion concentration in the electrolyte solution returning to the power generation element is substantially equal to the lithium ion concentration in the electrolyte solution located outside the power generation element.

  Here, in the conventional configuration, lithium ions having a lower concentration than the concentration of lithium ions when leaking from the power generation element return to the power generation element. That is, the lithium ion concentration in the power generation element cannot be returned to the concentration before the electrolyte leaks from the power generation element. In such a case, the concentration of lithium ions in the power generation element decreases, and the output performance of the lithium ion battery decreases.

  Therefore, in the present embodiment, as described above, the concentration of lithium ions in the electrolytic solution (second electrolytic solution) 20 as the surplus liquid is set to the electrolytic solution (first electrolytic solution) existing inside the power generation element 11. The concentration is higher than the lithium ion concentration. Thereby, even if the 1st electrolyte solution which exists in the inside of the electric power generation element 11 leaks outside, and mixes with the electrolyte solution 20 as a surplus liquid, it suppresses that the density | concentration of a lithium ion will be diluted. it can.

  And it can suppress that the density | concentration of the lithium ion contained in the electrolyte solution in the power generation element 11 falls by returning the electrolyte solution 20 located outside the power generation element 11 to the inside of the power generation element 11. . That is, since the electrolytic solution containing lithium ions having a higher concentration than the concentration of lithium ions contained in the electrolytic solution in the power generation element 11 returns to the inside of the power generation element 11, the concentration of lithium ions in the electrolytic solution in the power generation element 11 Can be suppressed.

  Here, as described above, the lithium ion concentration in the electrolytic solution 20 located outside the power generation element 11 is made substantially equal to the lithium ion concentration in the electrolytic solution leaking outside the power generation element 11 due to the deformation of the negative electrode layer 13b. be able to. Thereby, even if the electrolytic solution leaked to the outside of the power generation element 11 is mixed with the electrolytic solution 20, the concentration of lithium ions does not change.

  As described above, it is possible to prevent the output performance of the lithium ion battery 1 from being deteriorated by suppressing the decrease in the concentration of lithium ions in the power generation element 11.

  In addition, although the present Example demonstrated the case where the external force F when restraining a battery module acts with respect to the electric power generation element 11, it does not restrict to this. That is, the present invention can be applied as long as an external force that deforms the negative electrode layer 13 b is applied to the power generation element 11.

  In the present embodiment, as described in step S14 in FIG. 4, the first electrolyte remaining outside the power generation element 11 is discharged to the outside of the battery case 10. However, the present invention is not limited to this. Absent. Specifically, if the first electrolyte solution is injected into the battery case 10 in an amount to be included in the power generation element 11, the first electrolyte solution need not be discharged. In this case, since the total amount of the electrolytic solution to be injected into the battery case 10 is determined in advance, the second electrolysis is performed by an amount corresponding to the difference between the total amount and the amount of the injected first electrolytic solution. What is necessary is just to inject | pour a liquid.

It is a figure which shows the internal structure of a lithium ion battery. It is sectional drawing which shows the internal structure of a lithium ion battery. It is the schematic which shows the structure of an electric power generation element. It is a flowchart for demonstrating the process of inject | pouring electrolyte solution inside a battery case. It is a figure for demonstrating charging / discharging in a lithium ion battery. It is a figure for demonstrating the state which electrolyte solution leaks from a negative electrode layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Lithium ion battery 10: Battery case 11: Electric power generation element 12: Positive electrode element 12b: Positive electrode layer 13: Negative electrode element 13b: Negative electrode layer 12a, 13a: Current collecting plate 14: Separator 20: Electrolytic solution (excess liquid) 21: Positive electrode Terminal 22: Negative terminal

Claims (7)

A power generating element comprising a positive electrode element and a negative electrode element and comprising a first electrolyte;
A case for housing the power generation element;
A second electrolytic solution housed in the case and located outside the power generation element,
A lithium ion battery, wherein a concentration of lithium ions in the second electrolytic solution is higher than a concentration of lithium ions in the first electrolytic solution. The negative electrode element is formed on a current collector plate and has a negative electrode layer containing an active material,
2. The lithium ion battery according to claim 1, wherein the first electrolyte moves to the outside of the power generation element due to deformation of the negative electrode layer during discharge.   The lithium ion battery according to claim 2, wherein the negative electrode layer is deformed by receiving an external force for pinching the lithium ion battery.   The lithium ion concentration in the second electrolyte solution is substantially equal to the lithium ion concentration in the first electrolyte solution that moves to the outside of the power generation element due to deformation of the negative electrode layer. 3. The lithium ion battery according to 3. A power generation element including a positive electrode element and a negative electrode element is a method for producing a lithium ion battery in which a power generation element is accommodated in a case together with an electrolyte,
A first step of allowing the first electrolytic solution to be contained in the power generation element by injecting the first electrolytic solution into the case;
And a second step of injecting into the case a second electrolytic solution having a higher concentration of lithium ions than the concentration of lithium ions in the first electrolytic solution. . In the first step, the first electrolytic solution located outside the power generation element is discharged out of the case,
6. The method of manufacturing a lithium ion battery according to claim 5, wherein in the second step, an amount of the second electrolytic solution corresponding to a discharge amount of the first electrolytic solution is injected into the case. . The negative electrode element is formed on a current collector plate and has a negative electrode layer containing an active material,
The said 2nd electrolyte solution is substantially equal to the density | concentration of the lithium ion in the said 1st electrolyte solution which moves outside the said electric power generation element by the deformation | transformation of the said negative electrode layer at the time of discharge. The manufacturing method of the lithium ion battery as described.

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