A positive and negative common pole water-based supercapacitor electrode and a preparation method thereof

Abstract: in this paper, the material, formula, batching process and coating process of the water-based supercapacitor with positive and negative common poles were studied, and the electrode with good performance was prepared. The solid content and viscosity of negative slurry can reach 23% and 18Pas, with good uniformity. Through a coating process control, make the finished electrode has good adhesive properties and the surface resistance was lower, the positive surface resistance is about 1100 Ω, negative surface resistance is about 132 Ω; After the electrode is assembled, the working voltage of the water-based supercapacitor with positive and negative common poles can reach 1.6v, which is twice the working voltage of the traditional water-based supercapacitor and greatly improves the energy density of the supercapacitor.

Keywords: positive and negative common electrode water-based supercapacitor technology

One, foreword

Supercapacitors are also known as electrochemical capacitors [1-3], which are of great significance for starting, accelerating and driving uphill of electric vehicles. The extremely low specific energy of traditional supercapacitors makes it impossible for them to be used as the energy source of electric vehicles alone. Therefore, the specific power and specific energy of supercapacitors can be improved [4], making them have significant advantages as auxiliary energy [5]. It in the car when to start and climbing quickly provide high current and high power, in the normal driving by the main power supply quick charge, when the brake fast storage generator produces high current, it can reduce restrictions on large current charging battery of electric vehicle and greatly prolong the service life of battery, improve the electric car is practical, for the start of the fuel cell electric vehicle is. In the whole process of charging and discharging, supercapacitors have no chemical reaction, no high-speed rotation or other mechanical movement, no pollution to the environment [6], and no noise. They are simple in structure, light in weight and small in volume, making them more ideal energy accumulators.

In this paper, the electrode of a water-based supercapacitor with positive and negative common poles is studied. This electrode is used for assembly to obtain the supercapacitor [7-8], which has the biggest advantage of small internal resistance and high voltage. Its single working voltage can reach 1.6v, which is one times the voltage of traditional water-based supercapacitor.

Second, the experimental

The water-based supercapacitor with positive and negative common poles made by us is composed of four units, namely electrode, polypropylene film [9], electrolyte and shell. The electrodes are separated from each other by a membrane with ions blocking electrons for serial lamination, which is assembled into a metal shell, injected with electrolyte and sealed.

(1) electrode fabrication method

1. The ratio of positive and negative electrode materials and the preparation process of slurry

Adding binder (PTFE) to distilled water vacuum mixing tank, mixing 0.5 h make PTFE dispersed evenly, add the conductive agent SP (high tremie, Switzerland) and CNT slurry (Beijing day nai technology co., LTD., China) 2 h to stir fully dispersed, add manganese acid lithium (hunan shanshan technology co., LTD., China) stir 3 h form uniform anode paste, paste the final viscosity of 5 ~ 6.5 Pa. S, solid content is about 55%, material to join quality percentage for the LMO: PTFE: SP: CNT = 92:3:2:3. Adding CMC (model A30000, America) to distilled water vacuum mixing tank, mixing 2 h make CMC completely dissolved, add the conductive agent SP (high tremie, Switzerland) and CNT slurry (Beijing day nai technology co., LTD., China) stir 2 h to completely dispersed, then add activated carbon AC (specific surface area 2000 + 100 m2 / g, Shanghai of carbon material co., LTD.) 4 h to stir fully dispersed, add SBR (50% aqueous solution, shenzhen kuyt material co., LTD.) stir solution 1 h form uniform anode paste, The final viscosity of the slurry was 16 ~ 18pa.s, the solid content was about 25%, and the mass percentage of the material was AC: CMC: SP: CNT: SBR=90.5:2:2:3:2.5.

2. Manufacturing process of positive and negative common electrode

The positive and negative electrode slurry is coated on the coating machine of the special upper and lower layers of insulated baking oven. According to the technological requirements of positive electrode surface density (150 10) g/m2 and negative electrode surface density (268 5) g/m2, the positive and negative electrode slurry is coated on the same set of fluid to form the positive/negative common electrode.

(2) assembly method of water-based supercapacitors with positive and negative common poles

Then cut the qualified electrode coil into the size that meets the requirements of the process. Supercapacitor core is formed by superposition of 10 units in the series mode of "collecting fluid -- positive electrode -- diaphragm -- negative electrode -- collecting fluid -- positive electrode -- diaphragm", as shown in figure 1. The supercapacitor core is put into the shell, and the prepared electrolyte (lithium sulfate) is added. The shell is sealed with resin, and the sealed capacitor is squeezed under a 50T press. Finally, the capacitor is activated on the precision test equipment to form a positive and negative common pole water-based super capacitor, as shown in figure 2.

(3) testing of water-based supercapacitors with positive and negative common poles

After the assembled water-based supercapacitor with positive and negative common poles is charged and activated, it has the characteristics of supercapacitor. The quick adsorption and delinking realize the functions of quick charging and large current discharge of power supply.

The current of 1A was used to charge and discharge the supercapacitor, and its working voltage and energy density were obtained.

Iii. Results and discussion

(1) analysis of positive and negative common electrode

1. Good uniformity of negative paste

The uniformity of slurry directly affects the coating effect. Activated carbon has a relatively large specific surface area, resulting in a relatively low solid content of only about 20% and a relatively high viscosity of about 20pa.s when making slurry. The negative electrode slurry has a good fluidity when output, with a solid content of 23% and a viscosity of 18pa.s. During the coating process, the slurry will not be affected by external environmental factors, such as agglomeration, agglomeration, plug blade and so on.

2. Positive and negative common polar water-based electrode has good bonding characteristics

The traditional water-based electrode has the phenomenon of cracking in the process of coating and slag dropping in serious cases. However, the water-based electrode with positive and negative common poles produced by the process in this paper has good adhesion characteristics, which greatly reduces the contact resistance between the slurry and the collector, thus improving its polarization performance.

3. Low electrode surface resistance

The surface resistance of positive and negative common polar water-based electrode is small by strict control in material selection, batching process, coating process and so on. Using a multimeter measured the surface resistance and traditional water-based electrode surface resistance and measurement results show that the positive and negative of water-based electrode extremely positive electrode surface resistance is about 1100 Ω, the cathode surface resistance is about 132 Ω, traditional anode electrode surface resistance is about 3140 Ω, about 542 Ω cathode surface resistance.

(ii) test performance analysis of supercapacitors

FIG. 4 shows the test curve of the electrical performance of supercapacitors processed with water-based electrodes of positive and negative common poles made by us. The figure shows that the supercapacitor has a high voltage, and the single voltage can reach above 1.6v (the highest voltage can reach 1.8v), and the calculated energy density can reach 20Wh/kg (energy density E= 1/2cu2). Compared with the traditional water-based supercapacitor's voltage of 0.8v, its voltage is doubled. Four, conclusion

In this paper, a preparation method of water-based supercapacitor electrode with positive and negative common poles is studied, and the electrode obtained by this method has good performance. The test results showed that the solid content and viscosity of the negative slurry could reach 23% and 18000mpa.s, with good uniformity. Plus or minus total extremely good bonding performance of the electrode and the surface resistance is optimized, the positive surface resistance is about 1100 Ω, negative surface resistance is about 132 Ω; The single working voltage can reach above 1.6v, which is one time of the traditional water-based supercapacitor (0.8v), and the energy density can be greatly improved to reach 20Wh/kg.

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