JP5716543B2 - Lithium ion secondary battery and manufacturing method thereof - Google Patents

Description

The present invention relates to a lithium ion secondary battery including a negative electrode plate containing a metal salt of carboxymethyl cellulose (hereinafter also referred to as CMC-metal) in a negative electrode active material layer, and a method for producing the lithium ion secondary battery .

In recent years, lithium-ion secondary batteries (hereinafter also simply referred to as “batteries”) that can be charged and discharged have been used as driving power sources for vehicles such as hybrid vehicles and electric vehicles, and portable electronic devices such as notebook computers and video camcorders. Yes.
As such a battery, for example, a battery including a negative electrode plate containing a sodium salt of carboxymethyl cellulose (hereinafter also referred to as CMC-Na) together with negative electrode active material particles in a negative electrode active material layer is known (for example, a patent). Reference 1). CMC-Na is added for the purpose of increasing the viscosity of the paste when the negative electrode active material layer is formed using the paste.

JP 2005-228620 A

  However, since CMC which forms CMC-metal such as CMC-Na has a hydrophilic group, it easily absorbs moisture and easily releases metal ions in the presence of moisture. For this reason, in the battery of Patent Document 1, CMC-Na in the negative electrode active material layer easily takes in moisture in the battery case or in the electrolytic solution, for example. When a large amount of moisture is taken into the negative electrode active material layer due to the hygroscopicity of the CMC, the discharge capacity is smaller than the charge capacity, that is, the charge / discharge capacity ratio (= discharge capacity ratio, which is the ratio of the discharge capacity to the battery charge capacity). (Capacity / charge capacity × 100 (%)) becomes low. This is presumably because CMC is redissolved in water to form a film on the active material particles, or lithium ions react with water to deactivate lithium ions.

The present invention has been made in view of such a problem, and in a battery including a CMC metal salt in a negative electrode active material layer, a lithium ion secondary battery in which a decrease in charge / discharge capacity ratio is suppressed, and such An object of the present invention is to provide a method for manufacturing a lithium ion secondary battery .

One embodiment of the present invention is a battery including a negative electrode plate having a negative electrode current collector plate and a negative electrode active material layer formed on the negative electrode current collector plate and including a negative electrode active material particle and a metal salt of carboxymethyl cellulose. The negative electrode plate is a lithium ion secondary battery having a surface layer obtained by drying an aqueous solution containing an ammonium salt of carboxymethyl cellulose on the surface of the negative electrode active material layer.

In the battery described above, an aqueous solution containing an ammonium salt of carboxymethyl cellulose (hereinafter, also referred to as CMC-NH ₄ ) is formed on the surface of the negative electrode active material layer while having a CMC-metal in the negative electrode active material layer. A surface layer formed by drying is formed. For this reason, it can be set as the battery which suppressed the fall of charge / discharge capacity ratio. It is understood that the surface layer obtained by drying an aqueous solution of CMC-NH ₄ is less permeable to moisture and prevents moisture absorption of the negative electrode active material layer (CMC-metal).

In addition, since the basic structure of CMC-metal and CMC-NH _{4 in the} negative electrode active material layer is the same, the adhesion between the negative electrode active material layer having CMC-metal and the surface layer becomes good. There are also advantages.

Examples of the CMC-metal include CMC-Na, calcium salt of carboxymethyl cellulose (CMC-Ca), and lithium salt of carboxymethyl cellulose (CMC-Li).
Examples of the negative electrode active material particles include natural graphite particles such as flaky graphite and massive graphite, artificial graphite graphite (graphite) particles, and amorphous carbon particles.
Further, on the surface of the surface layer, for example, a heat-resistant layer (Heat composed of inorganic particles such as alumina, magnesia, zirconia, and silica and a binder such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). Resistance Layer (HRL) may be arranged.

Furthermore, in the above-described lithium ion secondary battery , the surface layer may be a lithium ion secondary battery having a layer thickness of 0.10 to 1.00 μm.

In a battery in which the thickness of the surface layer formed on the surface of the negative electrode active material layer is 0.10 μm or more, the charge / discharge capacity ratio can be sufficiently high, for example, 100% (the discharge capacity and the charge capacity are equal). It is considered that, by setting the layer thickness to 0.10 μm or more, it is possible to effectively prevent moisture from entering the negative electrode active material layer through this surface layer.
On the other hand, in a battery in which the layer thickness of the surface layer is 1.00 μm or less, the reaction resistance at a low temperature, for example, −30 ° C., can be reduced as compared with that having a layer thickness greater than 1.00 μm. This is considered to be because when the thickness of the surface layer is larger than 1.00 μm, the surface layer inhibits the transmission of lithium ions.
Thus, the above-described battery can be a battery having a small reaction resistance while reliably suppressing a decrease in charge / discharge ratio.

  In addition, as a measuring method of the layer thickness of the surface layer, for example, an elemental analysis is performed on the cross section of the negative electrode plate using a scanning electron microscope (SEM) or an X-ray microanalyzer (EPMA). And the method of measuring the thickness of the part in which the metal element (for example, Na) which makes the CMC-metal contained in a negative electrode active material layer does not exist among cross sections is mentioned.

Alternatively, another aspect of the invention includes a negative electrode plate having a negative electrode current collector plate and a negative electrode active material layer formed on the negative electrode current collector plate and containing negative electrode active material particles and a metal salt of carboxymethyl cellulose. A lithium ion secondary battery , wherein the negative electrode plate is a method for producing a battery having a surface layer obtained by drying an aqueous solution containing an ammonium salt of carboxymethyl cellulose on the surface of the negative electrode active material layer, a coating step of applying the aqueous solution of ammonium salt of carboxymethyl cellulose dissolved in water to the surface of the negative electrode active material layer, the lithium ion secondary battery and a drying step for evaporating the moisture in the coated the aqueous solution It is a manufacturing method.

  Since the above-described battery manufacturing method includes the above-described coating step and drying step, the surface layer can be easily and appropriately formed on the surface of the negative electrode active material layer.

Further, a method for manufacturing a lithium ion secondary battery described above, the aqueous solution has a viscosity, it may be a method for producing a lithium ion secondary battery as 300~700Pa · s.

When the viscosity of the aqueous solution is lower than 300 Pa · s, when the aqueous solution is applied to the surface of the negative electrode active material layer, the aqueous solution penetrates into the negative electrode active material layer, and the surface layer cannot be appropriately formed. On the other hand, when the viscosity is higher than 700 Pa · s, it is difficult to uniformly apply the aqueous solution on the surface of the negative electrode active material layer, and voids such as pinholes are easily generated in the formed surface layer.
In contrast, in the battery manufacturing method described above, the viscosity of the aqueous solution is in the range of 300 to 700 Pa · s, so that the aqueous solution can be uniformly applied to the surface of the negative electrode active material layer, and the surface of the negative electrode active material layer can be applied. A surface layer can be reliably formed.

It is a perspective view of the battery concerning an Example. It is a perspective view of the positive electrode plate of an Example. It is a perspective view of the negative electrode plate of an Example. It is the elements on larger scale of the negative electrode plate of an Example (A part in FIG. 3). It is explanatory drawing which shows the manufacturing method of the battery concerning embodiment.

Example 1
Next, Example 1 of the present invention will be described with reference to the drawings.
The battery 1 according to Example 1 will be described with reference to FIG.
This battery 1 is a lithium battery including an electrode body 10 in which a belt-like positive electrode plate 20 and a negative electrode plate 30 and a belt-like separator 40 interposed between the positive electrode plate 20 and the negative electrode plate 30 are wound in a flat shape. It is an ion secondary battery (see FIG. 1).
In this battery 1, the negative electrode plate 30 has a surface layer 36 described later on the surface (layer surface 31A) of a negative electrode active material layer 31 described later.
In addition, the battery 1 accommodates the electrode body 10 in the battery case 80, as shown in FIG.

  The battery case 80 has a battery case body 81 and a sealing lid 82 both made of aluminum. Among these, the battery case main body 81 has a bottomed rectangular box shape, and an insulating film (not shown) made of a resin and bent into a box shape is interposed between the battery case 80 and the electrode body 10. The sealing lid 82 has a rectangular plate shape, closes the opening of the battery case body 81, and is welded to the battery case body 81. Of the positive electrode current collector 91 and the negative electrode current collector 92 connected to the electrode body 10, the positive electrode terminal portion 91 </ b> A and the negative electrode terminal portion 92 </ b> A located at the tips of the sealing lid 82 penetrate, respectively. 1 protrudes from the lid surface 82a facing upward. Insulating members 95 made of insulating resin are interposed between the positive electrode terminal portion 91A and the negative electrode terminal portion 92A and the sealing lid 82 to insulate each other. Further, a rectangular plate-shaped safety valve 97 is also sealed on the sealing lid 82.

Moreover, the strip | belt-shaped separator 40 which comprises the electrode body 10 is a film form which consists of porous polyethylene (PE). The separator 40 has an electrolyte solution (not shown) formed by adding a solute (LiPF ₆ ) to a mixed organic solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in the battery 1 (electrode body 10). Impregnated.

Further, the thin plate-shaped positive electrode plate 20 is formed in a band shape along the edge of one side in the width direction (upper left in FIG. 2) of both the main surfaces of the band-shaped aluminum foil 28 and the aluminum foil 28. -It has the two positive electrode active material layers 21 and 21 arrange | positioned (refer FIG. 2).
Among these, the positive electrode active material layer 21 includes positive electrode active material particles made of LiNiCoMnO ₂ which is a lithium-containing composite oxide, a conductive auxiliary agent made of acetylene black, and a binder made of PVDF (see FIG. 2).

On the other hand, the thin plate-like negative electrode plate 30 is a belt-like copper foil 38 and a belt-like shape along the edge on one side in the width direction (upper left in FIG. 3) on both main surfaces of the copper foil 38. And two negative electrode active material layers 31 and 31 formed and arranged (see FIG. 3).
Among these, the negative electrode active material layer 31 contains the negative electrode active material particle which consists of natural graphite (lump graphite), and the sodium salt (CMC-Na) of carboxymethylcellulose (refer FIG. 3). In addition to these, a binder made of styrene butadiene rubber (SBR) is included (see FIG. 3). Among these, CMC-Na increases the viscosity V of the paste 31P when the negative electrode active material layer 31 is formed using the paste 31P, and also negative electrode active material particles or negative electrode active material layers 31 (negative electrode active material particles). And copper foil 38 are bound together.

  The negative electrode plate 30 has a surface layer 36 formed by drying an aqueous solution AQ (described later) containing an ammonium salt of carboxymethyl cellulose on the surface (layer surface 31A) of the negative electrode active material layer 31 (see FIG. 3). . In the battery 1 according to Example 1, the layer thickness T of the surface layer 36 is 0.50 μm (see FIG. 4). In addition, this layer thickness T is subjected to elemental analysis on the cross section of the negative electrode plate 30 using a scanning electron microscope (SEM). Obtained by measuring the thickness of the part.

The inventors conducted the following investigation on the characteristics of the battery 1 according to Example 1 described above.
First, the amount of water contained in the negative electrode plate 30 constituting the electrode body 10 was measured using the Karl Fischer method defined in JIS K 0068.
Specifically, a moisture measuring device (Aqua Counter AQ-7 manufactured by Hiranuma Sangyo Co., Ltd.) and a heating vaporizer (Hiranuma Sangyo Co., Ltd. manufactured) installed in a dry box having a dew point of −55 to −35 ° C. The water content of the negative electrode plate 30 was measured using an evaporator unit EV-6). In addition, the temperature in the heating vaporizer during measurement was kept at 180 ° C. Further, Hydranal R Aqualite RS-A (manufactured by SIGMA-ALDICH) was used as the solution, and high purity nitrogen (99.99%, manufactured by Daio Corporation) was used as the carrier gas. And it measured for 30 minutes by making the flow volume of carrier gas into 0.15 L / min (the unit of measurement of moisture content is micrograms).
Moreover, the negative electrode plate 30 (specifically, a cut piece obtained by cutting a portion formed by forming the negative electrode active material layer 31 on the copper foil 38 into 100 mm × 100 mm) left in a temperature environment of 25 ° C. in advance is used. It was.
The measurement results are shown in Table 1.

Next, a charge / discharge capacity ratio (= discharge capacity / charge capacity × 100 (%)) which is a ratio of the discharge capacity to the charge capacity of the battery 1 was measured.
Specifically, first, for a new (initial) battery 1 that has just been manufactured, in a temperature environment of 25 ° C., until the voltage of the battery 1 (voltage between terminals) becomes 4.2 V, 1/3 C Then, the battery was charged at a current value of 1 mm and charged for another hour while maintaining this voltage (constant current-constant voltage charging). The amount of electricity (charge amount) charged in the battery 1 by this constant current-constant voltage charge was measured, and this value was defined as the charge capacity.
Subsequently, under the same temperature environment of 25 ° C., constant current discharge is performed at a constant current value of 1/3 C until the voltage of the battery 1 reaches 3.0 V, and then the voltage is maintained at 3.0 V and 1 Discharge for hours (constant current-constant voltage discharge). The amount of electricity (charge amount) discharged from the battery 1 by this constant current-constant voltage discharge was measured, and this value was defined as the discharge capacity.
The value (percentage) obtained by dividing the discharge capacity by the charge capacity is taken as the charge / discharge capacity ratio and shown in Table 1 above.

(Comparative Examples 1 and 2)
On the other hand, each battery of Comparative Examples 1 and 2 was prepared, and the characteristics (moisture content of the negative electrode plate and charge / discharge capacity ratio) of each battery were measured in the same manner as the battery 1 of Example 1 described above. .
As shown in Table 1, the battery of Comparative Example 1 differs from the battery 1 in that it does not have a surface layer on the layer surface 31 </ b> A of the negative electrode active material layer 31. In addition, the battery of Comparative Example 2 has a surface layer (layer thickness is 0.50 μm, the same as that of the battery 1) obtained by drying an aqueous solution containing CMC-Na on the negative electrode active material layer 31 instead of the surface layer 36. It differs from the battery 1 of Example 1 by the point.
Table 1 also shows the moisture content of the negative electrode plate in each of the batteries of Comparative Examples 1 and 2 and the measurement results of the charge / discharge capacity ratio.

  According to Table 1, the moisture content of the negative electrode plate 30 of Example 1 is 200 ppm while the moisture content of the negative electrode plate according to Comparative Example 1 in which the surface layer is not formed is 1000 ppm. From this, it can be seen that the amount of moisture taken into the negative electrode active material layer 31 can be reduced by providing the surface layer 36 on the negative electrode active material layer 31. This is because, since CMC forming CMC-Na has a hydrophilic group, the negative electrode active material layer 31 containing CMC-Na easily absorbs moisture. However, the surface layer 36 formed on the surface of the negative electrode active material layer 31 has moisture. This is considered to be because the negative electrode active material layer 31 (CMC-Na) was prevented from absorbing moisture.

Moreover, the moisture content of the negative electrode plate concerning the comparative example 2 was 1230 ppm, and there was more moisture content of the negative electrode plate than Example 1 which has the surface layer 36, and the comparative example 1 which does not have a surface layer. In the negative electrode plate of Comparative Example 2, since the surface layer formed by drying the aqueous solution containing CMC-Na in addition to the negative electrode active material layer 31 containing CMC-Na is also easy to absorb moisture, the moisture content of the negative electrode plate is comparative. It is thought that it was more than 1.
Further, from the results of Example 1, Comparative Example 1 and Comparative Example 2, when the surface layer 36 is formed by drying an aqueous solution containing CMC-NH ₄ as in Example 1, moisture absorption is suppressed, and the negative electrode active material It can be seen that the amount of water in the layer 31 (CMC-Na) can be reduced.

In addition, the charge / discharge capacity ratios of the batteries of Example 1, Comparative Example 1 and Comparative Example 2 were 93%, 95% and 100%, respectively. From this, the battery of Comparative Example 2 having the largest moisture content of the negative electrode plate has the lowest charge / discharge capacity ratio, and conversely, the battery of Example 1 having the smallest moisture content of the negative electrode plate has the charge / discharge capacity. It can be seen that the ratio is high.
If a large amount of water is present in the negative electrode active material layer 31, CMC is re-dissolved in water to form a film on the active material particles, or lithium ions react with water to deactivate lithium ions. This is because the discharge capacity becomes smaller than the charge capacity.

As can be seen from the above, the surface formed by drying an aqueous solution containing CMC-NH ₄ on the layer surface 31A of the negative electrode active material layer 31 while having CMC-Na in the negative electrode active material layer 31 The battery 1 of Example 1 using the negative electrode plate 30 on which the layer 36 is formed can suppress a decrease in charge / discharge capacity ratio as compared with the batteries of Comparative Examples 1 and 2 described above.

(Examples 2, 3, 4, 5, 6)
Next, the batteries of Examples 2, 3, 4, 5, and 6 having different surface layer thicknesses T from Example 1 were prepared, respectively, and characteristics of these batteries (the moisture content of the negative electrode plate, and , Charge / discharge capacity ratio) was measured in the same manner as the battery 1. Specifically, the layer thicknesses T of the surface layers 36 in the batteries of Examples 2, 3, 4, 5, and 6 were 0.10, 1.00, 1.20, 1.50, and 0.05 μm, respectively. It was.
Table 1 also shows the measurement results of the moisture content of the negative electrode plate and the charge / discharge capacity ratio in each of the batteries of Examples 2 to 6.

Furthermore, about each battery of Examples 1-6 and Comparative Examples 1 and 2, the value of the reaction resistance of each battery under low temperature (-30 degreeC) was measured, respectively.
Specifically, first, using a power supply device (not shown), the voltage of each battery was adjusted to 3.65 V in a temperature environment of 25 ° C., and the state of charge (SOC) of each battery was adjusted to 50%.
After the adjustment, for each battery having a battery temperature of −30 ° C., the reaction resistance of each battery was measured by the AC impedance method (frequency is in the range of 10 ⁻¹ to 10 ⁵ MHz) using a Solartron electrochemical impedance measuring device. The value was measured. In addition, the value of the reaction resistance of each battery was calculated | required using the circular arc of the Cole-Cole plot obtained by the above-mentioned alternating current impedance method. That is, the distance (absolute value) from the origin of the complex plane where the Cole-Cole plot was performed to the intersection of the Cole-Cole plot and the x axis (electrical resistance) was taken as the value of the reaction resistance.
Table 1 shows the reaction resistance value of each battery.

According to Table 1, the moisture content of the negative electrode plate in Examples 2-6 is 190-500 ppm, and Examples 2-6 which have the surface layer 36 on the negative electrode active material layer 31 are the surface like Example 1. It can be seen that the amount of water in the negative electrode active material layer 31 is less than that of Comparative Example 1 (1000 ppm) having no layer.
Moreover, each charge / discharge capacity ratio of the batteries of Examples 2 to 6 was 97 to 100%. Each of Examples 2 to 6 having the surface layer 36 on the negative electrode active material layer 31 has a higher charge / discharge capacity ratio than Comparative Example 1 (95%) having no surface layer, as in Example 1. I understand.

Moreover, when looking at each expansion / discharge capacity ratio in the batteries of Examples 1 to 6, Examples 1 to 5 are 100%, while Example 6 is 97%. From this, in the batteries of Examples 1 to 5 in which the layer thickness T of the surface layer 36 is 0.10 to 1.50 μm, the discharge capacity and the charge capacity are equal, but the layer thickness T is smaller than 0.10 μm. It can be seen that the discharge capacity is smaller than the charge capacity.
From this, it can be seen that when the layer thickness T of the surface layer 36 is 0.10 μm or more, it is possible to more effectively prevent moisture from entering the negative electrode active material layer.

Moreover, among the batteries of Examples 1 to 6, in each of Examples 1 to 3 and 6, the reaction resistance value at −30 ° C. is the same 2500 mΩ, whereas each of Examples 4 and 5 In the battery, the reaction resistance values are 2750 mΩ and 3200 mΩ, respectively. From this, it can be seen that when the layer thickness T is larger than 1.00 μm, the value of the reaction resistance is increased.
This is considered to be because when the layer thickness T of the surface layer 36 is larger than 1.00 μm, the surface layer 36 inhibits lithium ion permeation at low temperatures.

As described above, in the battery 1 of Example 1 and the batteries of Examples 2 to 6, the negative electrode active material layer 31 has the CMC-Na in the negative electrode active material layer 31 but the layer of the negative electrode active material layer 31. A surface layer 36 formed by drying an aqueous solution containing CMC-NH ₄ is formed on the surface 31A. For this reason, it can be set as the battery 1 which suppressed the fall of charging / discharging capacity ratio, and each battery of Examples 2-6.
In addition, since CMC-Na _{4 in the} negative electrode active material layer 31 and CMC-NH ₄ forming the surface layer 36 have the same basic structure, the negative electrode active material layer 31 having CMC-Na and the surface layer There is also an advantage that the adhesiveness between the two is good.

Moreover, in each battery of the battery 1 and Examples 2 to 5 in which the layer thickness T of the surface layer 36 formed on the layer surface 31A of the negative electrode active material layer 31 is 0.10 μm or more, the charge / discharge capacity ratio is sufficiently high For example, it can be 100% (the discharge capacity and the charge capacity are equal).
On the other hand, in the battery 1 and the batteries of Examples 2, 3, and 6 in which the layer thickness T of the surface layer 36 was 1.00 μm or less, the reaction resistance at −30 ° C. was set to a layer thickness larger than 1.00 μm. It can be made smaller.
Thus, in the battery 1 of Example 1 and the batteries of Examples 2 and 3 in which the layer thickness T of the surface layer 36 is in the range of 0.10 to 1.00 μm, the decrease in the charge / discharge ratio is reliably suppressed. However, a battery having a low reaction resistance can be obtained.

Next, a method for manufacturing the battery 1 according to Example 1 will be described with reference to the drawings.
First, the negative electrode plate 30 is produced. Specifically, a paste (not shown) made by kneading negative electrode active material particles, a binder and CMC-Na in a solvent is applied to both main surfaces of the strip-shaped copper foil 38 by a known method. Then, the paste was dried.
Thereafter, the paste dried on both main surfaces of the copper foil 38 is compressed by a known technique, and the active material layer-carrying foil in which the negative electrode active material layers 31, 31 are supported on both the main surfaces of the copper foil 38. 30B was produced.

In the next coating process, a coating apparatus 110 shown in FIG. 5 is used. The coating apparatus 110 includes an unwinding unit 111, a die 115, and a winding unit 112.
Among these, the die 115 has a storage portion 116 that stores the aqueous solution AQ therein, and a discharge port that continuously discharges the aqueous solution AQ of the storage portion 116 toward the surface of the negative electrode active material layer 31 (layer surface 31A). 117. Among these, the discharge port 117 is slit-shaped and opens in parallel to the width direction (depth direction in FIG. 5) of the negative electrode active material layer 31.

In this coating step, first, an aqueous solution AQ having a viscosity V of 500 Pa · s was prepared. Specifically, 1 part by weight of CMC-NH ₄ and 99 parts by weight of water were respectively charged into the storage part 116, and CMC-NH ₄ was dissolved in water. The viscosity V of the aqueous solution AQ was measured using a rotational viscometer (for example, a B-type rotational viscometer) according to the method specified in JIS K 7117-2 (shear rate is 2 rpm).
Next, the strip-shaped active material layer carrying foil 30B wound in advance on the unwinding part 111 of the coating apparatus 110 is moved in the longitudinal direction DA from the unwinding part 151, and the negative electrode active material layer in the active material layer carrying foil 30B is moved. The aqueous solution AQ is applied to the layer surface 31A of 31 by the die 151. Thereby, the coating film 36 </ b> S made of the aqueous solution AQ is formed on the layer surface 31 </ b> A of the negative electrode active material layer 31.

Subsequently, in the drying process, the water in the coating film 36S is evaporated using the warm air dryer 120 shown in FIG. 5, and the coating film 36S is dried. Thus, the surface layer 36 was formed on the layer surface 31A of the negative electrode active material layer 31. After this drying step, the material is once wound around the winding unit 112.
Then, also about the layer surface 31A of the other negative electrode active material layer 31 of the active material layer carrying foil 30B, the above-mentioned coating film process and a drying process were performed, the surface layer 36 was formed, and the negative electrode plate 30 was produced (FIG. 3 and 4).

On the other hand, the positive electrode plate 20 constituting the electrode body 10 was produced by a known method (see FIG. 2).
Thereafter, the positive electrode plate 20 and the negative electrode plate 30 described above were wound together with the separator 40 described above to obtain the electrode body 10. Further, the positive electrode current collecting member 91 and the negative electrode current collecting member 92 are welded to the positive electrode plate 20 and the negative electrode plate 30, respectively. Thereafter, the electrode body 10 is accommodated in the battery case main body 81, and the battery case main body 81 is sealed by welding with the sealing lid 82. Then, an electrolytic solution was injected from a not-shown injection hole, and the injection hole was sealed to complete the battery 1 (see FIG. 1).

  Since the manufacturing method of the battery 1 of the first embodiment includes the above-described coating process and drying process, the surface layer 36 can be easily and appropriately formed on the layer surface 31A of the negative electrode active material layer 31.

Further, when the viscosity V of the aqueous solution AQ used in the coating process is lower than 300 Pa · s, the aqueous solution AQ is placed inside the negative electrode active material layer 31 when the aqueous solution AQ is applied to the layer surface 31A of the negative electrode active material layer 31. The surface layer 36 cannot be formed properly. On the other hand, when the viscosity V is higher than 700 Pa · s, it is difficult to uniformly apply the aqueous solution AQ on the layer surface 31A of the negative electrode active material layer 31, and voids such as pinholes are easily generated in the formed surface layer 36. .
On the other hand, in the manufacturing method of the battery 1 of Example 1, the viscosity V of the aqueous solution AQ was set to 500 Pa · s within the range of 300 to 700 Pa · s, and thus the aqueous solution AQ was applied to the layer surface 31A of the negative electrode active material layer 31. The surface layer 36 can be reliably formed on the layer surface 31 A of the negative electrode active material layer 31.

In the above, the present invention has been described with reference to the first to sixth embodiments. However, the present invention is not limited to the first embodiment and the like, and can be appropriately modified and applied without departing from the gist thereof. Needless to say.
For example, in Example 1 and the like, the negative electrode plate containing CMC-Na in the negative electrode active material layer is exemplified, but in addition to this CMC-Na, CMC-metal such as CMC-Ca and CMC-Li is used as the negative electrode active material layer. Examples of the negative electrode plate include.
In the first embodiment, only the surface layer 36 is provided on the negative electrode active material layer 31. However, for example, a heat resistant layer may be further provided on the surface of the surface layer 36. Examples of the heat-resistant layer include a layer made of inorganic particles such as alumina, magnesia, zirconia, and silica and a binder such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

1 Battery 30 Negative Electrode Plate 31 Negative Electrode Active Material Layer 31A Layer Surface (Surface of (Negative Electrode Active Material Layer))
36 Surface layer 38 Copper foil (Negative electrode current collector plate)
AQ aqueous solution T Layer thickness V Viscosity

Claims (4)

A negative electrode current collector plate;
And a negative electrode active material layer formed on the negative electrode current collector plate and containing a negative electrode active material particle and a metal salt of carboxymethyl cellulose.
A lithium ion secondary battery ,
The negative electrode plate is
On the surface of the negative electrode active material layer, there is a surface layer formed by drying an aqueous solution containing an ammonium salt of carboxymethyl cellulose.
Lithium ion secondary battery . The lithium ion secondary battery according to claim 1,
The surface layer is
The layer thickness is 0.10 to 1.00 μm
Lithium ion secondary battery . A negative electrode current collector plate;
And a negative electrode active material layer formed on the negative electrode current collector plate and containing a negative electrode active material particle and a metal salt of carboxymethyl cellulose.
A lithium ion secondary battery ,
The negative electrode plate is
On the surface of the negative electrode active material layer, a method for producing a battery having a surface layer obtained by drying an aqueous solution containing an ammonium salt of carboxymethyl cellulose,
An application step of applying an aqueous solution in which the ammonium salt of carboxymethyl cellulose is dissolved in water to the surface of the negative electrode active material layer;
And a drying step for evaporating water in the applied aqueous solution.
A method for producing a lithium ion secondary battery . It is a manufacturing method of the lithium ion secondary battery according to claim 3,
The aqueous solution is
The viscosity is 300 to 700 Pa · s.
A method for producing a lithium ion secondary battery .

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