JP6885272B2 - Electrode plate manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing an electrode plate including a band-shaped current collecting foil and a band-shaped electrode layer formed on the current collecting foil.

As an electrode plate used for a power storage device such as a lithium ion secondary battery and a lithium ion capacitor, an electrode plate including a band-shaped current collecting foil and a band-shaped electrode layer formed on the band-shaped current collecting foil is known. In such an electrode plate, for example, while transporting a band-shaped current collecting foil in the longitudinal direction, an electrode paste containing an active material, a solvent, etc. is applied to the current collecting foil, and a band-shaped coating is applied on the current collecting foil. Is formed, and then the coating film is heat-dried to form an electrode layer. As a prior art related to this, for example, Patent Document 1 can be mentioned.

Japanese Unexamined Patent Publication No. 2014-154363

By the way, the width direction dimension of the coating film formed in a band shape on the current collecting foil gradually decreases from immediately after the coating film is formed on the current collecting foil to the start of drying of the coating film. I've come to understand. This is because the coating film (electrode paste) formed on the current collector foil is repelled by the current collector foil. On the other hand, when the coating film starts to dry, the viscosity of the coating film increases and the coating film cannot move, so that it is considered that the decrease in the widthwise dimension of the coating film stops.

However, depending on the lot of the electrode paste and the lot of the current collector foil, the widthwise dimension of the coating film may be significantly reduced. In this case, the electrode layer may not be properly formed into a predetermined shape, for example, notch-shaped defect portions are formed at both ends in the width direction of the electrode layer. Therefore, it is conceivable to shorten the transport distance from the coating die for applying the electrode paste to the drying device for drying the coating film, but it is difficult to shorten the transport distance due to the limitation of the arrangement of each device.

The present invention has been made in view of the present situation, and has an electrode layer having stable width direction dimensions regardless of a lot of electrode paste or current collecting foil while maintaining a predetermined amount of the electrode layer. An object of the present invention is to provide a method for manufacturing an electrode plate capable of manufacturing an electrode plate.

One aspect of the present invention for solving the above problems is an electrode plate including a band-shaped current collecting foil and an electrode layer formed in a band shape on the current collecting foil along the longitudinal direction of the current collecting foil. In this manufacturing method, the electrode paste is discharged from the coating die toward the current collecting foil at a discharge rate of Q (m ³ / sec) to form a band-shaped coating film on the current collecting foil. A step and a drying step of drying the coating film to form the electrode layer are provided, and the coating step and the drying step carry the current collecting foil in the longitudinal direction at a transport speed V (m / min). In the coating process, the transport time T (sec) from immediately after the formation of the coating film to the start of drying and the surface tension γ (mN / m) of the electrode paste obtained in advance are performed. The contact angle θ (°) of the electrode paste in contact with the current collecting foil and the amount of decrease ΔW (mm) in the widthwise dimension W of the coating film that occurs from immediately after the formation of the coating film to the start of drying. Input surface tension γi (mN / mN /) based on the relational expression T = {ΔW- (A × γ) − (B × θ) + C} / D (however, A, B, C, and D are constants). The transport speed V (m / min) is controlled so that the reduction amount ΔW (mm) is equal to or less than a predetermined value ΔWa (mm) according to m) and the input contact angle θi (°). Manufacture of an electrode plate that controls the discharge amount Q (m ³ / sec) so that the coating amount M (mg / cm ² ) of the coating film maintains a predetermined predetermined amount Ma (mg / cm ^2). The method.

As a result of examination by the present inventor, the amount of decrease ΔW (mm) in the widthwise dimension W of the coating film is the transport time T (sec) from immediately after the formation of the coating film to the start of drying, and the surface tension γ (mN / mN /) of the electrode paste. It has been found that it can be expressed by a relational expression using m) and the contact angle θ (°) of the electrode paste in contact with the current collecting foil. Therefore, in order to suppress the reduction amount ΔW of the widthwise dimension W of the coating film to a predetermined value ΔWa (mm) or less, the surface tension γ (input surface tension) of the current collecting foil and the electrode paste to be used is used by using the above relational expression. Depending on γi) and the contact angle θ (input contact angle θi), the length of the transport time T from immediately after the formation of the coating film to the start of drying may be set to an appropriate value.

In order to change the transport time T, it is preferable to change the transport speed V (m / min) of the current collector foil. However, when the transport speed V is changed, the basis weight M (the basis weight of the electrode layer) (mg / cm ² ) of the coating film also changes. Specifically, the faster the transport speed V, the smaller the basis weight M (the basis weight of the electrode layer) of the coating film. Therefore, when the transport speed V is changed, the coating film from the coating die is changed according to the change in the transport speed V so that ^{the basis weight M of the coating film is maintained at a predetermined amount Ma (mg / cm 2).} The discharge amount Q (m ³ / sec) of the electrode paste may also be changed.

Therefore, in the above-mentioned method for manufacturing the electrode plate, the transfer time T, the surface tension γ of the electrode paste, the contact angle θ of the electrode paste in contact with the current collecting foil, and the amount of decrease ΔW in the widthwise dimension W of the coating film obtained in advance are obtained. Based on the relational expression of, the transport speed V of the collecting foil is such that the reduction amount ΔW of the widthwise dimension W of the coating film is equal to or less than a predetermined predetermined value ΔWa according to the input surface tension γi and the input contact angle θi. To control. Further, the discharge amount Q of the electrode paste from the coating die is controlled so that the basis weight M of the coating film maintains a predetermined predetermined amount Ma. As a result, it is possible to manufacture an electrode plate having an electrode layer having a stable width direction dimension W regardless of the lot of the electrode paste or the lot of the current collecting foil while keeping the amount of the electrode layer in a predetermined amount.
Further, in the above-mentioned method for manufacturing the electrode plate, T = {ΔW− as the relational expression of the transport time T (sec), the surface tension γ (mN / m), the contact angle θ (°) and the reduction amount ΔW (mm). Since (A × γ) − (B × θ) + C} / D is used, an electrode plate having an electrode layer having a stable widthwise dimension W can be manufactured more appropriately.

It is a perspective view of the positive electrode plate which concerns on embodiment. It is a flowchart of the manufacturing method of the positive electrode plate which concerns on embodiment. It is explanatory drawing which shows the state of forming the coating film by using the coating apparatus which concerns on embodiment. It is explanatory drawing which shows the state of forming the coating film by using the coating apparatus, and then heating-drying the coating film by using a drying apparatus which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a perspective view of a positive electrode plate (electrode plate) 1 according to the present embodiment. In the following description, the longitudinal direction EH, the width direction FH, and the thickness direction GH of the positive electrode plate 1 are defined as the directions shown in FIG. The positive electrode plate 1 is specifically used for manufacturing a square and sealed lithium ion secondary battery mounted on a vehicle such as a hybrid car, a plug-in hybrid car, or an electric vehicle. It is a strip-shaped positive electrode plate used for manufacturing a mold electrode body.

The positive electrode plate 1 has a current collecting foil 3 made of a strip-shaped aluminum foil extending in the longitudinal direction EH. The first electrode layer 5 is formed in a band shape on the region extending in the center of the width direction FH and in the longitudinal direction EH in the first main surface 3a of the current collector foil 3. Further, the second electrode layer 6 is formed in a band shape on the region extending in the center of the width direction FH and in the longitudinal direction EH in the second main surface 3b on the opposite side of the current collector foil 3. The first electrode layer 5 and the second electrode layer 6 are a positive electrode active material (lithium transition metal composite oxide in this embodiment), a conductive material (acetylene black in this embodiment), and a binder (polyfluorine in this embodiment). Kabiniriden) consists of. The widthwise dimension W (mm) of the first electrode layer 5 and the second electrode layer 6 of the present embodiment is a stable value regardless of the lot of the current collecting foil 3 or the lot of the electrode paste DP described later. .. In the present embodiment, the width direction dimension W of the first electrode layer 5 and the second electrode layer 6 is W = 200 mm.
At both ends of the positive electrode plate 1 in the width direction FH, the first electrode layer 5 and the second electrode layer 6 are not present in the thickness direction GH, respectively, and the current collecting foil 3 is exposed in the thickness direction GH. It is 1 m.

Next, a method for manufacturing the positive electrode plate 1 will be described (see FIGS. 2 to 4). The electrode paste DP used for forming the first electrode layer 5 and the second electrode layer 6 is prepared in advance. Specifically, a positive electrode active material (lithium transition metal composite oxide in this embodiment), a conductive material (acetylene black in this embodiment), and a binder (polyvinylidene fluoride in this embodiment) are used as a solvent (this embodiment). In the form, it is kneaded with N-methyl-2-pyrrolidone) to obtain an electrode paste DP.

Then, first, in the "first coating step S1", the electrode paste DP is applied onto the first main surface 3a of the current collector foil 3 by using the coating apparatus 100 (see FIGS. 3 and 4). A coating film 5x is formed. The positive electrode plate having the first coating film 5x on the current collector foil 3 is also referred to as “undried one-side positive electrode plate 1x”.
The coating apparatus 100 includes a coating die 110 that applies the electrode paste DP on the current collecting foil 3, a backup roll 120 that conveys the current collecting foil 3, and a pump 130 that sends the electrode paste DP to the coating die 110. , Control to control the transport speed V (m / min) of the collecting foil 3 and the discharge amount Q (m ³ / sec) of the electrode paste DP from the coating die 110 and the tank 140 for storing the electrode paste DP. A unit 150 is provided.

Of these, the coating die 110 has a die discharge portion 111, a manifold 113, and the like. The die discharge portion 111 is located at the tip of the coating die 110 (on the right side in FIG. 4), and is a portion that discharges the electrode paste DP toward the current collector foil 3 conveyed by the backup roll 120 described later. .. Further, the manifold 113 is a portion where the electrode paste DP supplied from the tank 140 by the pump 130 is temporarily stored.

The backup roll 120 has a diameter of 250 mm and is arranged at a position facing the die discharge portion 111 of the coating die 110 (in FIG. 4, immediately to the right of the die discharge portion 111). By rotating the roll 120 clockwise in FIGS. 3 and 4, the current collecting foil 3 wound around the backup roll 120 is conveyed in the longitudinal direction EH. The rotation speed n (rpm) of the backup roll 120, that is, the transport speed V (m / min) of the current collector foil 3, is controlled by the control unit 150 described later.

The pump 130 is installed in the middle of the supply pipe 160 of the electrode paste DP connecting the coating die 110 and the tank 140. By controlling the pump 130 with the control unit 150, the supply amount of the electrode paste DP supplied from the pump 130 to the coating die 110, that is, the electrode paste DP discharged from the coating die 110 toward the current collector foil 3. The discharge amount Q (m ³ / sec) is controlled.

In the control unit 150, the amount of decrease ΔW (mm) in the widthwise dimension W of the first coating film 5x is predetermined in accordance with the input input surface tension γi (mN / m) and the input contact angle θi (°). The rotation speed n (rpm) of the backup roll 120 and therefore the transport speed V (m / min) of the current collecting foil 3 are controlled so as to be equal to or less than a predetermined value ΔWa (mm). At the same time, the control unit 150 controls the discharge amount Q (coating) of the pump 130 so that ^{the basis weight M (mg / cm 2} ) of the first coating film 5x maintains a predetermined predetermined amount Ma (mg / cm ^{2). The discharge amount Q) (m 3} / sec) of the electrode paste DP from the die 110 is controlled.

Specifically, the control unit 150 uses the surface tension γ (input surface tension γi) (mN / m) of the electrode paste DP used by the operator and the electrode paste DP in contact with the current collector foil 3 to be used. It is configured so that each value of the contact angle θ (input contact angle θi) (°) can be input.
Then, when the operator inputs the input surface tension γi and the input contact angle θi to the control unit 150, the control unit 150 receives the transport time T (from immediately after the formation of the first coating film 5x obtained in advance to the start of drying). sec), the surface tension γ (mN / m) of the electrode paste DP, the contact angle θ (°) of the electrode paste DP in contact with the current collecting foil 3, and between immediately after the formation of the first coating film 5x and the start of drying. The required transport speed V (m / min) of the current collecting foil 3 is calculated by using the following relational expression with the reduction amount ΔW (mm) of the widthwise dimension W of the first coating film 5x generated in.
(Relational expression)
T = {ΔW- (A × γ)-(B × θ) + C} / D
(However, A, B, C, and D are constants, respectively)

The transport distance L (mm) from the position where the first coating film 5x is formed by the coating die 110 to the position where the first coating film 5x starts to dry (the inlet of the drying device 200) is constant (this). In the embodiment, L = 1.3 m). Further, the required rotation speed n (rpm) of the backup roll 120 is calculated from the transport speed V (m / min).
^{Next, the control unit 150 obtains the discharge amount (discharge amount of the pump 130) Q (m 3} / sec) of the electrode paste DP from the coating die 110 according to the calculated transfer speed V (m / min).

In the present embodiment, the constants A to D of the above relational expression are set to A = 0.0159, B = 0.0170, C = 1.2482, and D = 0.1580. Further, the reduction amount ΔW (target reduction amount ΔWa) of the widthwise dimension W of the first coating film 5x that occurs from immediately after the formation of the first coating film 5x to the start of drying is set to ΔW = ΔWa = 0.2 mm. That is, the following relational expression was used as the relational expression.
T = (0.2000-0.0159 x γ-0.0170 x θ + 1.2482) /0.1580
In the present embodiment, the constants A to D are the transport time T from immediately after the formation of the first coating film 5x to the start of drying, the surface tension γ of the electrode paste DP, and the electrode paste in contact with the current collecting foil 3. It is a value obtained by performing multiple regression analysis using a large number of experimental results in which the contact angle θ of DP is changed and the amount of decrease ΔW in the width direction dimension W of the first coating film 5x is measured.

When the operator inputs the values of the input surface tension γi and the input contact angle θi to the control unit 150, the control unit 150 sets the transfer time T (sec) from the above relational expression to the required transfer speed V (m / m /). In addition to min), the required rotation speed n (rpm) of the backup roll 120 is calculated. Then, according to the instruction of the control unit 150, the backup roll 120 is rotated at this rotation speed n (rpm).

Further, when the transport speed V (m / min) of the current collector foil 3 is changed, the basis weight M (mg / cm ² ) of the first coating film 5x also changes. Therefore, the electrodes are subjected to changes in the transport speed V (m / min) so that the textured amount M (mg / cm ² ) of the first coating film 5x maintains a predetermined predetermined amount Ma (mg / cm ^2). The discharge amount Q (m ³ / sec) of the paste DP is also changed. Specifically, based on the relational expression of Q = a × V (where a is a constant), for example, when the transport speed V (m / min) becomes 1.1 times, the discharge amount Q of the electrode paste DP is Q. (M ³ / sec) is also 1.1 times. Then, according to the instruction from the control unit 150, the pump 130 is operated so that the ^{discharge amount Q (m 3 / sec) is obtained.}

The first coating step S1 is performed using such a coating apparatus 100, and the electrode paste DP is applied onto the first main surface 3a of the current collector foil 3 to form the first coating film 5x. Specifically, the electrode paste DP is applied from the die discharge portion 111 of the coating die 110 toward the first main surface 3a of the current collector foil 3 which is conveyed by the backup roll 120 at a transfer speed V (m / min). The first coating film 5x is continuously formed in a strip shape on the first main surface 3a of the current collector foil 3 by discharging at a discharge rate Q (m ^{3 / sec).}

Prior to the first coating step S1, the surface tension γ (input surface tension γi) (mN / m) of the electrode paste DP of the lot used for manufacturing and the electrode paste of the lot above were applied to the current collecting foil 3 of the lot used for manufacturing. The contact angles θ (input contact angles θi) (°) when the DPs are brought into contact with each other are investigated. Then, the input surface tension γi (for example, γ1 = 30 mN / m) and the input contact angle θi (for example, θ1 = 45 °) are input to the control unit 150 of the coating apparatus 100.

Then, from the above-mentioned relational expression, that is, T = (0.2000-0.0159 × γ-0.0170 × θ + 1.2482) /0.1580, the transfer time T = 1.3 sec can be obtained by the control unit 150. Further, as described above, since the transport distance L is L = 1.3 m, the required transport speed V can be obtained as V = 60 m / min. Further, as described above, since the diameter of the backup roll 120 is 250 mm, the required rotation speed n of the backup roll 120 can be obtained as n = 76.4 rpm from this transport speed V = 60 m / min. Therefore, the control unit 150 rotates the backup roll 120 at this rotation speed n (rpm).

Further, in the present embodiment, Ma = based on the solid content excluding the solvent so that the coating amount M (mg / cm ² ) of the first coating film 5x maintains a predetermined predetermined amount Ma (mg / cm ^{2). The discharge amount Q (m 3} / sec) of the electrode paste DP corresponding to the transport speed V (m / min) can be obtained so as to maintain 5.0 mg / cm ^2. In the example of this embodiment, the discharge amount Q of the electrode paste DP is Q = 8.7 × 10 ^-6 m ³ / sec. Then, the control unit 150 ^{operates so that the discharge amount Q (m 3} / sec) of the pump 130 becomes this value.

When any lot of the electrode paste DP and the current collecting foil 3 used for manufacturing is switched to a new lot, the operator sets the input surface tension γi and the input contact angle θi of the new lot to the control unit 150. Re-enter. As a result, the electrode paste DP and the current collector foil 3 of the new lot are also ^{coated with the appropriate rotation speed n (rpm) of the backup roll 120 and the discharge amount Q (m 3} / sec) of the pump 130, and the width is widened. The reduction amount ΔW (mm) of the directional dimension W is controlled to 0.2 mm or less.

After the first coating step S1 is completed, then in the "first drying step S2", the first coating film 5x on the first main surface 3a of the current collector foil 3 is dried to form the first electrode layer 5. .. Specifically, the undried single-side positive electrode plate 1x on which the first coating film 5x is formed on the current collector foil 3 is conveyed into the drying device 200, and hot air is blown to the first coating film 5x of the undried single-side positive electrode plates 1x. The first coating film 5x is heated and dried to form the first electrode layer 5. As a result, the one-sided positive electrode plate 1y having the first electrode layer 5 is formed on the first main surface 3a of the current collector foil 3.

Next, in the "second coating step S3", the electrode paste DP is applied on the second main surface 3b of the current collecting foil 3 of the positive electrode plate 1y on one side to form the second coating film 6x. The formation of the second coating film 6x is also performed in the same manner as in the first coating step S1 by using the coating apparatus 100 described above. At this point, the dried first electrode layer 5 is formed on the first main surface 3a of the current collector foil 3, and the undried second coating film is formed on the second main surface 3b of the current collector foil 3. 6x is formed. This positive electrode plate is also referred to as "undried double-sided positive electrode plate 1z".

After the second coating step S3 is completed, the second coating film 6x is dried to form the second electrode layer 6 in the “second drying step S4”. Specifically, the undried double-sided positive electrode plate 1z on which the second coating film 6x is formed is conveyed into the drying device 200, and hot air is blown to the second coating film 6x of the undried double-sided positive electrode plates 1z to perform the second coating. The film 6x is heated and dried to form the second electrode layer 6. As a result, the positive electrode plate 1w having the current collecting foil 3, the first electrode layer 5, and the second electrode layer 6 is formed.

Next, in the "pressing step S5", the above-mentioned positive electrode plate 1w is pressed by a roll press machine (not shown) to increase the densities of the first electrode layer 5 and the second electrode layer 6, respectively. Thus, the positive electrode plate 1 is completed.

As described above, in the method for manufacturing the positive electrode plate 1, the transport time T, the surface tension γ of the electrode paste DP, the contact angle θ of the electrode paste DP in contact with the current collecting foil 3, and the first coating film obtained in advance are used. Based on the relational expression of the amount of decrease ΔW in the width direction dimension W of the film 5x and the second coating film 6x, the width direction of the first coating film 5x and the second coating film 6x according to the input surface tension γi and the input contact angle θi. The transport speed V of the current collecting foil 3 is controlled so that the reduction amount ΔW of the dimension W is equal to or less than a predetermined value ΔWa, which is set in advance. Further, the discharge amount Q of the electrode paste DP from the coating die 110 is controlled so that the basis weight M of the first coating film 5x and the second coating film 6x maintains a predetermined predetermined amount Ma. As a result, the first electrode layer 5 and the second electrode layer 6 have a stable width direction dimension W, regardless of the lot of the electrode paste DP or the lot of the current collecting foil 3, while keeping the amount M of the first electrode layer 5 and the second electrode layer 6 at a predetermined amount Ma. A positive electrode plate 1 having one electrode layer 5 and a second electrode layer 6 can be manufactured. In particular, in the present embodiment, since T = {ΔW− (A × γ) − (B × θ) + C} / D is used as the above-mentioned relational expression, the first electrode layer 5 having a stable width direction dimension W and The positive electrode plate 1 having the second electrode layer 6 can be manufactured more appropriately.

Although the present invention has been described above in accordance with the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments and can be appropriately modified and applied without departing from the gist thereof.
For example, in the embodiment, the manufacturing method of the positive electrode plate 1 is exemplified as the manufacturing method of the electrode plate, but the present invention can also be applied to the manufacturing method of the negative electrode plate.

1 Positive electrode plate (electrode plate)
3 Current collector foil 5 1st electrode layer 5x 1st coating 6 2nd electrode layer 6x 2nd coating DP Electrode paste 100 Coating device 110 Coating die 120 Backup roll 130 Pump 150 Control unit 200 Drying device γ (Electrode paste) () Surface tension γi Input surface tension θ (of the electrode paste in contact with the current collecting foil) Contact angle θi Input contact angle W (of the first coating film and the second coating film) Width direction dimension ΔW (first coating film and second coating film) Decrease amount ΔWa (in the width direction dimension of the coating film) Predetermined value (target reduction amount)
T (collecting foil) transport time L (collecting foil) transport distance V (collecting foil) transport speed Q (electrode paste from coating die) discharge amount M (first coating and second coating) Amount of coating (of film) Ma (Amount of coating) Predetermined amount S1 First coating step S2 First drying step S3 Second coating step S4 Second drying step

Claims (1)

A method for manufacturing an electrode plate comprising a band-shaped current collecting foil and an electrode layer formed in a band shape on the current collecting foil along the longitudinal direction of the current collecting foil.
A coating process in which the electrode paste is discharged from the coating die toward the current collecting foil at a discharge rate of Q (m ³ / sec) to form a strip-shaped coating film on the current collecting foil.
A drying step of drying the coating film to form the electrode layer is provided.
The coating process and the drying process
The current collecting foil is continuously transported in the longitudinal direction at a transport speed of V (m / min).
The above coating process is
The transport time T (sec) obtained in advance from immediately after the formation of the coating film to the start of drying, the surface tension γ (mN / m) of the electrode paste, and the contact angle θ of the electrode paste in contact with the current collecting foil. (°) and the relational expression T = {ΔW− (A × γ) − ( Based on B × θ) + C} / D (however, A, B, C, and D are constants)
The transport speed is such that the reduction amount ΔW (mm) is equal to or less than a predetermined value ΔWa (mm) according to the input input surface tension γi (mN / m) and the input contact angle θi (°). Controls V (m / min) and
A method for manufacturing an electrode plate that controls the discharge amount Q (m ³ / sec) so that the basis weight M (mg / cm ² ) of the coating film maintains a predetermined predetermined amount Ma (mg / cm ^2).

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