ADDITIVE FOR ELECTROCHEMICAL ELEMENT POSITIVE ELECTRODE, COMPOSITION FOR ELECTROCHEMICAL ELEMENT POSITIVE ELECTRODE INCLUDING SAID ADDITIVE, AND ELECTROCHEMICAL ELEMENT

Abstract

The present invention relates to an additive for an electrochemical element positive electrode comprising an activated carbon, wherein the activated carbon has a specific surface area in accordance with BET method of 1300-2500 m.sup.2/g, a pore volume of pores having a diameter of 2 nm or more of 0.35 cm.sup.3/g or less, a pore volume of pores having a diameter less than 2 nm of 0.5 cm.sup.3/g or more, and an ash content of 0.5% by weight or less.

Claims

1. An additive for an electrochemical element positive electrode comprising an activated carbon, wherein the activated carbon has a specific surface area in accordance with BET method of 1300-2500 m.sup.2/g, a pore volume of pores having a diameter of 2 nm or more of 0.35 cm.sup.3/g or less, a pore volume of pores having a diameter less than 2 nm of 0.5 cm.sup.3/g or more, and an ash content of 0.5% by weight or less.

2. The additive for an electrochemical element positive electrode according to claim 1, wherein the activated carbon has an oxygen content of 1.3% by weight or more and 3% by weight or less, and a hydrogen content of 0.33% by weight or more and 0.55% by weight or less.

3. The additive for an electrochemical element positive electrode according to claim 1, wherein the activated carbon has an average particle size of 2 μm to 20 μm.

4. A slurry stabilizer for an electrochemical element positive electrode comprising the additive for an electrochemical element positive electrode according to claim 1.

5. A composition for an electrochemical element positive electrode comprising: the additive for an electrochemical element positive electrode according to claim 1; and a positive electrode active material, wherein a content of the additive for an electrochemical element positive electrode is 10% by weight or less with respect to a total weight of the positive electrode active material.

6. The composition for an electrochemical element positive electrode according to claim 5, further comprising: a binder in an amount of 0.5 to 10% by weight with respect to a total solid content of the composition for an electrochemical element positive electrode.

7. The composition for an electrochemical element positive electrode according to claim 5, further comprising: a conductive material in an amount of 1 to 10% by weight with respect to a total solid content of the composition for an electrochemical element positive electrode.

8. An electrochemical element, comprising: an electrochemical element positive electrode, wherein the positive electrode comprises a layer comprising the composition for an electrochemical element positive electrode according to claim 5.

9. The electrochemical element according to claim 8, wherein the electrochemical element operates from 2V to 5V.

10. The electrochemical element according to claim 8, wherein the electrochemical element is a non-aqueous electrolyte secondary battery.

Description

EXAMPLES

[0132] Hereinafter, examples and comparative examples will be described. However, the following examples are merely one example, and the concepts of the present invention are not limited to the following examples.

(Specific Surface Area by Nitrogen Adsorption BET Method)

[0133] An approximate equation derived from a BET equation is described below.

p/[v(p.sub.0−p)]=(1/v.sub.mc)+[(c−1)/v.sub.mc](p/p.sub.0)  [Math. 1]

[0134] By using the approximate equation, v.sub.m is obtained by substituting an actually measured adsorption amount(v) at a predetermined relative pressure(p/p.sub.0) by a multi-point method according to nitrogen adsorption at the liquid nitrogen temperature, and the specific surface area (SSA: in m.sup.2/g) of the sample was calculated by the following equation.

[00001]$\begin{array}{cc}\mathrm{Specific}\mathrm{surface}\mathrm{area}=\left(\frac{v_m\mathrm{Na}}{22400}\right)\times {10}^{-18}& \left[\mathrm{Math}.2\right]\end{array}$

[0135] In the equation, v.sub.m is the adsorption amount (cm.sup.3/g) required for forming a monomolecular layer on a sample surface, v is the actually measured adsorption amount (cm.sup.3/g), p.sub.0 is the saturated vapor pressure, p is the absolute pressure, c is the constant (reflecting the adsorption heat), N is the Avogadro's number 6.022×10.sup.23, and a (nm.sup.2) is the area occupied by adsorbate molecules on the sample surface (molecular occupied cross-sectional area).

[0136] Specifically, the amount of nitrogen adsorption to the activated carbon at the liquid nitrogen temperature was measured by using “Autosorb-iQ-MP” manufactured by Quantachrome as follows. After the activated carbon used as a measurement sample was filled in a sample tube and the sample tube was cooled to −196° C., the pressure was once reduced, and nitrogen (purity: 99.999%) was then adsorbed to the measurement sample at a desired relative pressure. An adsorbed gas amount v was defined as an amount of nitrogen adsorbed to the sample when the equilibrium pressure was reached at each desired relative pressure.

(Pore Volume)

[0137] The adsorption isotherm obtained from the measurement of the nitrogen adsorption amount was analyzed by the NL-DFT method, and a volume of pores having a pore size (pore diameter) less than 2 nm and volume of pores having a pore size (pore diameter) of 2 nm or more and 50 nm or less are calculated as the micropore volume and the mesopore volume, respectively.

(Elemental Analysis)

[0138] Elemental analysis was performed by using the oxygen/nitrogen/hydrogen analyzer EMGA-930 manufactured by HORIBA, Ltd.

[0139] The detection methods of the analyzer are oxygen: inert gas fusion-non-dispersive infrared absorption method (NDIR), nitrogen: inert gas fusion-thermal conductivity method (TCD), and hydrogen: inert gas fusion-non-dispersive infrared absorption method (NDIR) calibrated with an (oxygen/nitrogen) Ni capsule, TiH.sub.2 (H standard sample), and SS-3 (N, O standard sample), and 20 mg of a sample having moisture content measured at 250° C. for about 10 minutes for a pretreatment was put into an Ni capsule and measured after 30 seconds of degasification in the elemental analyzer. The test was performed by analyzing three specimens, and an average value was used as an analysis value.

(Average Particle Diameter by Laser Scattering Method)

[0140] The average particle diameter (particle size distribution) of plant-derived char and the activated carbon was measured by the following method. The sample was put into an aqueous solution containing 5 weight % surfactant (“Toriton X100” manufactured by Wako Pure Chemical Industries), treated by an ultrasonic cleaner for 10 minutes or more, and dispersed in the aqueous solution.

[0141] The particle size distribution was measured by using this dispersion. Particle size distribution measurement was performed by using a particle diameter/particle size distribution measuring device (“Microtrac MT3000 EXII” manufactured by MicrotracBEL). D50 is the particle diameter at which the cumulative volume is 50%, and this value was used as the average particle diameter.

(Ash Content Measurement Method)

[0142] The weight of an alumina crucible that was dummy heated at 900° C. and allowed to cool in a desiccator containing silica gel is measured. After vacuum drying for 8 to 10 hours in a constant temperature dryer adjusted to 120° C., 20 g of an activated carbon that was allowed to cool in a desiccator containing silica gel as a desiccant was placed in an alumina crucible with a volume of 50 ml, and the crucible+activated carbon weight was accurately measured to 0.1 mg. The alumina crucible containing the sample was placed in an electric furnace with dry air introduced into the electric furnace at 20 L/min and the temperature was raised to 200° C. in 1 hour. Then the temperature was raised to 700° C. over 2 hours and kept at 700° C. for 14 hours and the sample was incinerated. After the incineration was completed, the crucible was allowed to cool in a desiccator containing silica gel, the crucible+ash weight was accurately measured to 0.1 mg, and the ash content was calculated from the following formula.

Ash content (weight %)={(crucible+ash weight)−(crucible weight)/(crucible+activated carbon weight)−(crucible weight)}×100  [Math.3]

(Composition for Lithium Ion Secondary Battery Positive Electrode or Slurry for Lithium Ion Secondary Battery Positive Electrode)

[0143] 30 parts by weight of N-methylpyrrolidone solution in which 3 parts by weight of polyvinylidene fluoride (KF Polymer 7200 manufactured by Kureha Corporation) is dissolved, 93 parts by weight of LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 (“cellSeed C-5H” manufactured by Nippon Chemical Industrial Co., Ltd) as a positive electrode active material, 2 parts by weight of acetylene black (“Denka Black” manufactured by Denki Kagaku Kogyo Co., Ltd) as a conductive material, and 2 parts by weight of an activated carbon prepared in Examples and Comparative Examples described later was added and mixed, the composition was stirred and dispersed with a homomixer (4500 rpm) manufactured by Primix Co., Ltd, while N-methylpyrrolidone is appropriately added so that the solid content concentration of the composition becomes 50% by weight, then a composition for a lithium ion secondary battery positive electrode or slurry for a lithium ion secondary battery positive electrode was obtained.

(Lithium Ion Secondary Battery Positive Electrode)

[0144] The above composition for a lithium ion secondary battery positive electrode or slurry for a lithium ion secondary battery positive electrode was applied onto an aluminum foil (“1N30-H”, manufactured by Fuji Kako Co., Ltd.) as a current collector by using a bar coater (“T101”, manufactured by Matsuo Sangyo Co., Ltd) and dried by a hot air drier (manufactured by Yamato Scientific co., Ltd) at 80° C. for 30 minutes. After primary drying, rolling treatment was performed by using a roll press (manufactured by Hosen Corp.). Then, after punching as a lithium ion secondary battery positive electrode (014 mm), a lithium ion secondary battery positive electrode was produced by secondary drying under a reduced pressure condition at 120° C. for 3 hours. The water content at this time were measured by taking the prepared and dried electrode (ϕ14 mm), heating to 250° C. by a Karl Fischer (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) and measuring the water content under a nitrogen stream. The water content was controlled to be 20 ppm or less so that the added activated carbon was able to exert the action other than water absorption.

(Production of Lithium Ion Secondary Battery)

[0145] The above lithium ion secondary battery positive electrode was transferred to a glove box (manufactured by Miwa Manufacturing Co., Ltd.) in an argon gas atmosphere. For a negative electrode, a laminate consisting of a metal lithium foil (thickness 0.2 mm, φ16 mm) as a positive electrode active material layer and a stainless steel foil (thickness 0.2 mm, φ17 mm) as a current collector was used. In addition, a polypropylene-based (cell Guard #2400, manufactured by Polypore) separator is used, and as an electrolyte, a mixed solvent system in which ethylene carbonate (EC) of lithium hexafluorophosphate (LiPF.sub.6) and ethylmethyl carbonate (EMC) are added with vinylene carbonate (VC) (1M-LiPF.sub.6, EC/EMC=3/7 volume %, VC 2 weight %) was used to inject and a coin-type lithium ion secondary battery (2032 type) was produced.

1. Additive for Lithium Ion Secondary Battery Positive Electrode

Example 1

[0146] A char (specific surface area: 370 m.sup.2/g) produced from a coconut shell from Philippines was subjected to primary activation at 850° C. for 2 hours using propane combustion gas+water vapor (partial pressure of water vapor: 25%). Then, it was acid-washed with hydrochloric acid (concentration: 0.5 N, diluent: ion-exchanged water) at a temperature of 85° C. for 30 minutes, and then sufficiently washed with ion-exchanged water to remove the residual acid, and dried to obtain a primary activated granular activated carbon. Further, a heat treatment at 700° C. was carried out for 1 hour in a nitrogen atmosphere. This granular activated carbon was finely pulverized so that the average particle size was 6 μm to obtain an activated carbon.

Example 2

[0147] A primary activated granular activated carbon was obtained by washing with acid and water as well as drying in the same manner as in Example 1. This granular activated carbon was further subjected to secondary activation at 970° C. for 2 hours using propane combustion gas (partial pressure of water vapor 15%) to obtain a granular activated carbon. The obtained secondary activated granular activated carbon was further washed with acid and water as well as dried, and then a heat treatment at 700° C. was carried out for 1 hour in a nitrogen atmosphere to obtain a secondary washed granular activated carbon. This granular activated carbon was finely pulverized so that the average particle size was 6 μm to obtain an activated carbon.

Example 3

[0148] The activation time of Example 1 was extended to 3 hours to obtain a primary activated granular activated carbon having a specific surface area of 1810 m.sup.2/g. This granular activated carbon was further subjected to secondary activation at 970° C. using propane combustion gas (partial pressure of water vapor 15%) to obtain a granular activated carbon. The obtained secondary activated granular activated carbon was further washed with acid and water as well as dried, and then a heat treatment at 700° C. was carried out for 1 hour in a nitrogen atmosphere to obtain a secondary washed granular activated carbon. Except for the above, an activated carbon was obtained in the same manner as in Example 1.

Example 4

[0149] Example 4 was prepared in the same manner as in Example 1, except that the activated carbon was discharged into a flow vessel with nitrogen having a purity of 99.99% upon the heat treatment discharge, and allowed to cool to 200° C. or lower in a nitrogen gas atmosphere.

[0150] This granular activated carbon was finely pulverized so that the average particle size was 6 pm to obtain an activated carbon.

Example 5

[0151] A primary activated granular activated carbon was obtained in the same manner as in Example 1. This granular activated carbon was further subjected to secondary activation using propane combustion gas+water vapor (partial pressure of water vapor 15%) at 970° C. until achieving the following specific surface area to obtain a secondary activated granular activated carbon having a specific surface area of 2252 m.sup.2/g. The obtained secondary activated granular activated carbon was further washed with acid and water as well as dried, and then a heat treatment at 700° C. was carried out for 1 hour in a nitrogen atmosphere to obtain a secondary washed granular activated carbon. This granular activated carbon was finely pulverized so that the average particle size was 6 μm to obtain an activated carbon.

Example 6

[0152] The same procedure as in Example 1 was carried out, and the activated carbon was obtained in the same manner as in Example 1 except that the granular activated carbon was finely pulverized so that the average particle size was 2.4 μm.

Comparative Example 1

[0153] An activated carbon was obtained in the same manner as in Example 1 except that the washing with acid was not performed in Example 1.

Comparative Example 2

[0154] An activated carbon was obtained in the same manner as in Example 1 except that the primary activation temperature was set to 920° C. in Example 1.

[0155] The physical characteristics of the activated carbons obtained in Examples and Comparative Examples are shown in Table 1.

TABLE-US-00001 TABLE 1 Specific surface Average Elemental area Mesopore Micropore particle analysis Ash (BET) volume volume size [weight %] content [m.sup.2/g] [cm.sup.3/g] [cm.sup.3/g] [μm] O H [weight %] Example 1 1685 0.07 0.60 5.70 2.047 0.561 0.19 Example 2 2184 0.17 0.86 5.59 2.422 0.508 0.32 Example 3 1834 0.11 0.72 5.82 1.453 0.352 0.03 Example 4 1686 0.06 0.57 5.88 1.478 0.508 0.22 Example 5 2259 0.16 0.83 5.55 1.447 0.496 0.17 Example 6 1571 0.08 0.62 2.35 2.044 0.537 0.21 Comparative 1605 0.06 0.57 6.05 3.122 0.555 0.67 Example 1 Comparative 1246 0.66 0.32 7.15 3.343 0.612 0.21 Example 2

Examples 7 to 12 and Comparative Examples 3 to 4

[0156] By using the activated carbons obtained in Examples 1 to 6 and Comparative examples 1 to 2, a lithium ion secondary battery was prepared according to the above description. For each lithium ion secondary battery obtained, a charge-discharge test was conducted using a charge-discharge tester (“TOSCAT” manufactured by Toyo System Co., Ltd.) after measuring the DC resistance value before the initial charge. As for the DC resistance, the resistance value when 0.5 mA was passed for 3 seconds was measured. Lithium doping was performed to a level of 1 mV relative to the lithium potential at a rate of 70 mA/g with respect to the weight of the active material. A constant voltage of 1 mV relative to the lithium potential was further applied for 8 hours, and the doping was terminated thereafter. The capacity (mAh/g) at this point was defined as the charge capacity. Subsequently, dedoping was performed to a level of 2.5 V relative to the lithium potential at a rate of 70 mA/g with respect to the weight of the active material, and the capacity discharged at this point was defined as the discharge capacity. The percentage of discharge capacity/charge capacity was defined as the charge-discharge efficacy (initial charge-discharge efficiency) and was used as an index of the utilization efficiency of lithium ions in the battery. In addition, the irreversible capacity was calculated by subtracting the discharge capacity from the charge capacity. The results obtained are shown in Table 2.

Comparative Example 5

[0157] A lithium ion secondary battery was prepared and its characteristics were measured in the same manner as in Example 7 except that an activated carbon was not added. The results obtained are shown in Table 2.

TABLE-US-00002 TABLE 2 DC resistance Additive for Charge Discharge Irreversible Initial (before positive capacity capacity capacity charge-discharge charge) electrode mAh/g mAh/g mAh/g efficiency % (Ω) Example 7 Example 1 185 157 28 85 203 Example 8 Example 2 185 158 27 85 188 Example 9 Example 3 185 156 29 84 212 Example 10 Example 4 185 155 30 84 232 Example 11 Example 5 185 157 28 85 167 Example 12 Example 6 186 158 28 85 158 Comparative Comparative could not charge Example 3 Example 1 Comparative Comparative 181 147 34 81 689 Example 4 Example 2 Comparative None 185 153 32 83 609 Example 5

[0158] From the results in Table 2, it was found that when the additive for an electrochemical element positive electrode of the present invention was used, the DC resistance was low and the conductivity of the positive electrode was improved. In addition, it was found that the efficiency of lithium ion utilization in the battery was improved since the initial charge/discharge efficiency was high and the irreversible capacity was low. Meanwhile, when the activated carbon of Comparative Example 1 in which the ash content does not meet the range of the present invention was used, the lithium ion secondary battery was short-circuited and the battery characteristics could not be measured. Further, when the activated carbon of Comparative Example 2 whose specific surface area and pore volume do not meet the range of the present invention was used, the DC resistance was higher than that of Comparative Example 3 in which the activated carbon is not included, and the initial charge/discharge efficiency and other battery characteristics were also inferior.

2. Slurry Stabilizer for Lithium Ion Secondary Battery Positive Electrode

Example 13

[0159] A char (specific surface area: 370 m.sup.2/g) produced from coconut shell from Philippines was subjected to primary activation at 850° C. for 2 hours using propane combustion gas+water vapor (partial pressure of water vapor: 25%). Then, it was acid-washed with hydrochloric acid (concentration: 0.5 N, diluent: ion-exchanged water) at a temperature of 85° C. for 30 minutes and then sufficiently washed with ion-exchanged water to remove the residual acid and dried. Then, a heat treatment at 700° C. was carried out for 1 hour in a nitrogen atmosphere. This granular activated carbon was finely pulverized so that the average particle size was 6 pm to obtain an activated carbon.

Example 14

[0160] A primary activated granular activated carbon was obtained by washing with acid and water as well as drying in the same manner as in Example 13. This granular activated carbon was further subjected to secondary activation at 970° C. using propane, combustion gas (partial pressure of water vapor 15%) to obtain a granular activated carbon. The obtained secondary activated granular activated carbon was further washed with acid and water as well as dried, and then a heat treatment at 700° C. was carried out for 1 hour in a nitrogen atmosphere to obtain a secondary washed granular activated carbon. This granular activated carbon was finely pulverized so that the average particle size was 6 pm to obtain an activated carbon.

Example 15

[0161] The activation time of Example 13 was extended to 3 hours to obtain a primary activated granular activated carbon having a specific surface area of 1810 m.sup.2/g. This granular activated carbon was further subjected to secondary activation at 970° C. using propane combustion gas (partial pressure of water vapor 15%) to obtain a granular activated carbon. The obtained secondary activated granular activated carbon was further washed with acid and water as well as dried, and then a heat treatment at 700° C. was carried out for 1 hour in a nitrogen atmosphere to obtain a secondary washed granular activated carbon. Except for the above, an activated carbon was obtained in the same manner as in Example 13.

Example 16

[0162] Example 16 was prepared in the same manner as in Example 13, except that the activated carbon was discharged into a flow vessel with nitrogen having a purity of 99.99% upon the heat treatment discharge, and allowed to cool to 200° C. or lower in a nitrogen gas atmosphere. This granular activated carbon was finely pulverized so that the average particle size was 6 pm to obtain an activated carbon.

Example 17

[0163] A primary activated granular activated carbon was obtained in the same manner as in Example 13. This granular activated carbon was further subjected to secondary activation using propane combustion gas+water vapor (partial pressure of water vapor 15%) at 970° C. until achieving the following specific surface area to obtain a secondary activated granular activated carbon having a specific surface area of 2252 m.sup.2/g. The obtained secondary activated granular activated carbon was further washed with acid and water as well as dried, and then a heat treatment at 700° C. was carried out for 1 hour in a nitrogen atmosphere to obtain a secondary washed granular activated carbon. This granular activated carbon was finely pulverized so that the average particle size was 6 pm to obtain an activated carbon.

Example 18

[0164] The same procedure as in Example 13 was carried out, and the activated carbon was obtained in the same manner as in Example 13 except that the granular activated carbon was finely pulverized so that the average particle size was 2.4 pm.

Comparative Example 6

[0165] An activated carbon was obtained in the same manner as in Example 13 except that the heat treatment temperature was 830° C. in Example 13.

Comparative Example 7

[0166] An activated carbon was obtained in the same manner as in Example 13 except that the primary activation temperature of was set to 920° C. in Example 13.

Comparative Example 8

[0167] An activated carbon was obtained in the same manner as in Example 14 except that the secondary activation temperature was set to 870° C. in Example 14.

[0168] The physical characteristics of the activated carbons obtained in Examples and Comparative examples are shown in Table 3.

TABLE-US-00003 TABLE 3 Specific surface Average Elemental area Mesopore Micropore particle analysis Ash (BET) volume volume size [weight %] content [m.sup.2/g] [cm.sup.3/g] [cm.sup.3/g] [μm] O H [weight %] Example 13 1685 0.07 0.60 5.70 2.047 0.561 0.19 Example 14 2184 0.17 0.86 5.59 2.422 0.508 0.32 Example 15 1834 0.11 0.72 5.82 1.453 0.352 0.03 Example 16 1686 0.06 0.57 5.88 1.478 0.508 0.22 Example 17 2259 0.16 0.83 5.55 1.447 0.496 0.17 Example 18 1571 0.08 0.62 2.35 2.044 0.537 0.21 Comparative 1220 0.05 0.52 5.74 2.025 0.572 0.2 Example 6 Comparative 1246 0.66 0.32 7.15 3.343 0.612 0.21 Example 7 Comparative 1570 0.03 0.49 7.22 2.561 0.512 0.4 Example 8

Examples 19 to 24 and Comparative Examples 9 to 12

[0169] By using the activated carbons obtained in Examples 13 to 18 and Comparative Examples 6 to 8, a slurry for a lithium ion secondary battery positive electrode and lithium ion secondary battery were prepared according to the above description. For each lithium secondary battery obtained, a charge-discharge test was conducted using a charge-discharge tester (“TOSCAT” manufactured by Toyo System Co., Ltd.). Lithium doping was performed to a level of 1 mV relative to the lithium potential at a rate of 70 mA/g with respect to the weight of the active material. A constant voltage of 1 mV relative to the lithium potential was further applied for 8 hours, and the doping was terminated thereafter. The capacity (mAh/g) at this point was defined as the charge capacity. Subsequently, dedoping was performed to a level of 2.5 V relative to the lithium potential at a rate of 70 mA/g with respect to the weight of the active material, and the capacity discharged at this point was defined as the discharge capacity. The percentage of discharge capacity/charge capacity was defined as the charge-discharge efficacy (initial charge-discharge efficiency) and was used as an index of the utilization efficiency of lithium ions in the battery. In addition, the irreversible capacity was calculated by subtracting the discharge capacity from the charge capacity. The results obtained are shown in Table 4.

(Coatability Evaluation)

[0170] The coatability of the composition for a lithium ion secondary battery positive electrode obtained above was evaluated according to the followings. As described above, after drying the coated electrode with hot air at 80° C. for 30 minutes, the case if there are no traces of bubbles or agglomerates on the coated surface was evaluated as ⊚, the case if there are no agglomerates but are traces of bubbles was evaluated as ∘, the case if a small amount of agglomerates was observed was evaluated as Δ, and the case if the agglomerates were observed everywhere was evaluated as x. The results obtained are shown in Table 4.

Comparative Example 12

[0171] A lithium ion secondary battery was prepared and its characteristics were measured in the same manner as in Example 19 except that an activated carbon was not added. The results obtained are shown in Table 4.

TABLE-US-00004 TABLE 4 Charge Discharge Irreversible Initial Slurry capacity capacity capacity charge-discharge stabilizer Coatability mAh/g mAh/g mAh/g efficiency % Example 19 Example 13 ⊚ 185 157 28 84.9 Example 20 Example 14 ⊚ 185 158 27 85.4 Example 21 Example 15 ◯ 185 156 29 84.3 Example 22 Example 16 ◯ 185 155 30 83.8 Example 23 Example 17 ◯ 185 157 28 84.9 Example 24 Example 18 ◯ 186 158 28 84.9 Comparative Comparative Δ 186 154 32 82.8 Example 9 Example 6 Comparative Comparative X 181 147 34 81.2 Example 10 Example 7 Comparative Comparative Δ 182 146 36 80.2 Example 11 Example 8 Comparative None X 185 153 32 82.9 Example 12

[0172] From the results in Table 4, when the slurry stabilizer for an electrochemical element positive electrode of the present invention was used, it was found that the slurry coatability is excellent, and that in the lithium ion secondary battery produced by using the slurry stabilizer thereof, the battery characteristics were excellent. Meanwhile, when an activated carbon that does not meet the scope of the present invention was used or when an activated carbon is not contained as a slurry stabilizer, the slurry coatability was poor and the battery characteristics of the obtained lithium ion secondary battery was also poor.