PERFORMANCE CHARACTERIZATION OF NICD BATTERY BY ARBIN BT2000 ANALYZER IN BATAN

Transcription

1 MATERIALS SCIENCE and TECHNOLOGY Edited by Evvy Kartini et.al. PERFORMANCE CHARACTERIZATION OF NICD BATTERY BY ARBIN BT2000 ANALYZER IN BATAN H. Jodi, E. Kartini, T. Nugraha Center for Technology of Nuclear Industry Material BATAN, Puspiptek, Serpong, Indonesia ABSTRACT Early 2010, the Center for Technology of Nuclear Industry Material (PTBIN) BATAN has acquired a new Battery Analyzer, i.e. the ARBIN BT2000. This device is crucial for supporting our research program on the development of new rechargeable battery. In order to test its performance, a series of experiments were performed using a commercial non-branded 700mAh NiCd battery. These measurements include several tests namely charge-discharge, life cycle and cyclic voltammetry, which are important for understanding performance of the battery. It took 547 s for the battery to be fully-charged with a charge rate of 0.2C from 1.145V to 1.376V, while for the discharge with a rate of 0.05C from 1.305V to 0.75V, it took 54.8s. After the first 36 life cycle tests, the capacity tends to drop slightly. Reduction peaks were observed at 1.132V with a current of 175mA at cycle 50 of Cyclic Voltammetry test with a scan rate of 1mV/s. It is concluded that this NiCd battery shows a fair standard performance, and also the ARBIN device has a great potential and capability to analyze battery performances. Keywords : Battery Analyzer, NiCd, performance characterization INTRODUCTION A battery is a device that converts chemical energy to electrical energy, providing a convenient source of portable energy with wide uses in countless consumer electronic products. The basic unit of battery consists of an anode (negative electrode), a cathode (positive electrode) and an electrolyte, that is a solution through which ions move but not the electron. The electrochemical oxidation-reduction reaction inside a battery during discharge involves the transfer of electrons from the anode that is oxidized, to the cathode that is reduced [1]. NiCd battery is rechargeable battery that uses Cadmium metals as the anode, and Nickelic Hydroxide as the cathode, with a solution of Potassium Hydroxide as the Electrolyte. Upon discharge, the cathode undergoes a reduction to Nickelous Hydroxide Ni(OH) 2, and the anode is oxidized to produce Cadmium Hydroxide Cd(OH) 2 [2]. This work was aimed to test the performance of a new device that BBIN Laboratory of PTBIN-BATAN has just acquired. The tests would serve as preliminary experiments to analyze the work and performance of the battery tester. The newly added device is BT2000 Battery Analyzer from ARBIN Instrument Company. BT2000 has multiple, independently controlled potentiostat/ galvanostat channels that can run different tests simultaneously. The software package MITS-PRO 4.0 which are running under MS Windows XP operating system, uses a distributed system control for automatic or manual maintenance and also

2 Materials Science and Technology filters to reduce the fluctuation of current and voltage. The model currently has 4 channels with a voltage range of -10V to +10V that can provide a maximum charge/discharge of 10A, current ranges of 10A/1A/0.1A and a maximum channel power of 50W. The equipment has all types of necessary control functions to test all types of battery chemistry for its performance characteristics based on current/voltage through the function featured[3]. A NiCd battery was used as the object of this work because this type of batteries is one of the most standard rechargeable battery, very popular and numerous brands of them are currently commercially available in the Jakarta area. By performing the common performance tests of the battery, the group hopes to acquire the skill to operate and to further explore the features available in the device, as well as to obtain the characteristics of the tested battery. EXPERIMENTAL This experiments were carried out at BBIN Laboratory of PTBIN-BATAN, from May to June 2010 using a 4 channel ARBIN BT2000 Battery Analyzer. 2 pieces of a non-branded AA size 700mAh NiCd battery with a diameter of 14 mm and a height of 50.5 mm were used as the object of the experiment. A series of experiments were carried out including chargedischarge, life cycle and cyclic voltammetry tests to analyze performance of the battery[3-5]. Charge-discharge and cyclic voltametry tests were applied to the first battery, while life cycle test was applied to second one. Charging tests were performed by applying constant current rates until the battery was fully charged, while discharge tests were done by applying negative constant-current rate, with decreasing voltage until it reached a fixed value. Life cycle test is a series of chargedischarge test cycle. One cycle consist of a full-charge and a full-discharge process. The cycle is repeated several times. Cyclic Voltammetry tests were performed by scanning the voltage between two voltages and observing the current. The voltage was swept from the first one with a fix scan rate and, when it reached the second voltage, the scan is reversed and the voltage is swept back to the first one. The process was repeated for several cycles. RESULTS AND DISCUSSION A new battery was charged by using a constant current rate of 0.2C to a state of fully charged. Fully charged state is indicated by negative delta voltage, that is when the voltage is not increasing again while current is applied, rather it start to form a flat curve or even decreased. Charge curve of the battery is shown in Figure 1(a). Charging process was started from voltage of 1.145V which indicated that the battery only was partially charged from the factory, or that it had lost part of its charge during storage prior to being purchased. The battery was fully charged at a voltage of V after subjected to 547s of charging process. Charge capacity of the system was 21.3 mah or equivalent to energy of 28.8 mwh. This capacity was just about 3% of the nominal capacity of the battery. It is very natural because to increase the voltage by as small as 0.231V, the applied current was large, so it no need a longer time for the battery to become fully charged, and consequently the capacity is relatively small too. Discharge test was performed by applying negative constant current rate of 0.05C. The discharge curve of the battery is shown in figure 1(b). The battery was discharged from 1.305V to a terminal voltage of 0.75V during s of discharge time. Capacity of the process was 533.6mAh, or an equivalent to energy to mwh, that is about 76.24% of battery nominal capacity. When the battery attained 1.00V discharge capacity was 74.96% of nominal capacity, an reached additional 0.8% when it reached 0.95V, and then further additional 0.2% at 0.93V, and the rest 0.28% of the capacity occurred betweent V. 356

3 Performance Characterization of NiCd Battery The delta capacity was turned around x10-2 mah/s in the range of 1.27V 0.93V but started to fall after it surpassed 0.93V, and it approached 2.0x10-4 mah/s at 0.75V. Consequently in the range of V, the capacity remaining was very small. So it was clear that the battery was fully discharged when it reached voltage about V. Figure 1: (a). Charge curve of NiCd battery. 700mAh battery was charged by constant current rate of 0.2C and fully charged at 1.378V after 547 s with capacity of 21.3 mah. (b). Discharge curve of NiCd battery. The battery was discharged by constant current rate of 0.05C from 1.305V to 0.75V. The capacity was mah. Life cycle test was performed by repeating a series of charge-discharge cycle test. The battery was charged with constant current rate of 0.25C (~175 ma) to its fully-charged state, and then discharged by applying negative constant current rate of -0.05C (~35 ma) until the voltage was down to 0.95V (full-discharge). The cycle was repeated 65 times continuously. Total test time was 339,315s. Figure 2 shows life cycle curve of the battery for cycles 6 to 10. From this process of charge-discharge cycle, we observed behaviour of charge (discharge) time and charge (discharge) capacity of every cycle. In the beginning of the process it took 487.6s to fully charg the battery. This charge time increased with increment of cycle number, and reached a peak value of s at the 36 th cycle. After the 36 th cycle, charge time became unstable, but tended to slow down, and had a value of 660.4s at the end of the test i.e. 65 th cycle. Charge time occured to discharge time, but the value was larger almost 5 times due to the discharge rate was smaller 5 times than the one of charging process. In the beginning of the process, discharge time was s, peaked at cycle 36 of s, tends to slow down afterward and had a value of s at cycle 65. Figure 2: Life cycle curve of 700mAh NiCd battery at cycle 6 to 10. Since the capacity is the current multiplied by the process time, the behaviour of capacity is similar to that of time. Charge capacity was 23.7mAh at the first cycle, peaked to 357

4 Materials Science and Technology 54.5mAh at cycle 36, and 32.1mAh at cycle 65. While discharge capacity was 21.8mAh during the first cycle, peaked to 54.4mAh at cycle 36, and 32.1mAh at cycle 65. It was clear that discharge capacity have same value with charge capacity. Although the capacity (charge time) tended to increase after cycle 36, maximum voltage that indicated that the battery was fully charged did not follow that trend, and reached a value of 1.578V at cycle 65. This unstable capacity change while the voltage was still rising indicated that performance of the battery began to degrade, due to several causes like the battery chemistry, or even the memory effect. The capacity and discharge time behavior is shown in figure 3(a) while figure 3(b) shows maximum voltage reached in the charging process at every cycle. Figure 3: (a) The capacity and discharge time in every cycle of life cycle test. The capacity and time peaked at cycle 36, and afterwards tend to decrease. (b) maximum voltage and charge time in every cycle of test. Maximum voltage of charging process in every cycle is tends to increase while the time tends to slow down after cycle of 36. Cyclic voltammetry tests were performed by scanning the voltage of the battery from 0.95V to 1.55V, and was swept back to 0.95V with a scan rate dv/dt = 1 mv/s. In this experiment, the cycle was repeated 55 times. Cyclic voltammogram that demonstrated voltage dependence upon current at cycle 50 is shown in Figure 4. Figure 4: Cyclic Voltammogram of 700mAh NiCd battery which scanned from 0.95 V to 1.55V with scan rate of V/s at cycle 50. Reduction peaks clearly seen at 1.132V, but Oxidation peaks was not observed. Reduction peaks were observed at negative scanning process, but at positive scanning process oxidation peaks could not be observed. During the positive scan from 0.95V to 1.55V, the applied potential became sufficiently positive at V to cause oxidation of Ni(OH) 2 to form NiOOH that would occur at the cathode surface. While at the anode surface reduction 358

5 Performance Characterization of NiCd Battery of Cd(OH) 2 occurred to the metallic Cadmium. This oxidation was accompanied by anodic current which increased as the voltage became increasingly positive, but it continued after the direction of voltage scan was switched to negative scanning, until the applied potential becomes sufficiently negative to cause reduction of NiOOH to form Ni(OH) 2. The reduction was signaled by cathodic current at about 1.371V. The current increases as the voltage became increasingly negative, and peaked at V, and then decreased. The current at the peak was ma. Since characteristics of voltammogram depends on a number of factors including chemical reactivity of the electroactive species, the electron transfer rate, and the voltage scan rate, and the fact that the applied voltage could alter the energy of the electron within the metal electrode, the oxidation peaks might be observed either by performing tests at higher voltage range, or by the application of higher voltage scan rate. The cyclic voltammetry tests were performed for 55 cycles at the same voltage scan rate, to see the behavior of peaks, and to obtain accurate peaks of current. Figure 5 shows the position of reduction peaks and its current in every cycle of the test. At the first test, the position of reduction peaks was 1.179V, and it shifted down as cycle number increases, 1.144V at cycle 5, and then tends to became stable at about 1.132V after cycle 15. The current also showed the same behaviour. Current at 88.3 ma was observed at the first cycle, then increased to ma at cycle 5, and then tended to stabilize at about ma, after cycle 15. So, at scan rate of 1mV/s for this NiCd system, the stabilized voltamogram formed after performing 15 cycles with reduction peak of 1.132V, and reduction current of 175 ma. Figure 5: Position of reduction peaks and its current in every cycle of cyclic voltammetry test. The position and its current tend to stabil after cycle 15 of cyclic voltammetry test. Based on the performance test results, it could be clearly seen that ARBIN BT2000 device was capable of characterizing the performance of the battery by showing us the basic character of fairly standard commercially available NiCd battery. For the future, we have to explore the capability of the device because many performance characteristics of a battery can also be studied including current/voltage staircases, current/voltage pulses, current/voltage simulations, internal resistances/impedances, capacity rates, power, load and other profile based on current/voltage through the function features. CONCLUSION Test performance for the characterization of a commercial NiCd battery was carried out by the ARBIN BT2000 Battery Analyzer, including the charge-discharge tests, as well as life cycle and cyclic voltametry tests. The capability of this device can still be explored in the future by using many other features of the current-voltage based performance tests. Test performance of the battery resulted in fair performance of the commercially available NiCd 359

6 Materials Science and Technology batteries. At current-rate of 0.2C, the capacity utilized to charge the battery from 1.145V to 1.376V was very small that was 21.3mAh, while during discharge from 1.305V to 0.75V at current-rate 0.05C, the capacity was 533.6mAh. The capacity needed to charge-discharge the battery peaked between cycles 36 to 65 during the life cycle tests. Stabilized voltamogram was obtained after performing 15 cycles of the voltametry test. Reduction peak occurred at 1.132V, but oxidation peak was not observed. ACKNOWLEDGMENT This work is funded by Indonesian Ministry of Research & Technology under The Incentive Program of Development of New Rechargeable Battery. REFERENCES [1]. Manuel F. Almeida, et.al, Waste Management, 26, (2006) [2]. D. Berndt, Maintenance-Free Batteries, Research Studies Press, Ltd (1993) [3]. Arbin Instruments, MITS Pro 4.0-BT2000 User Manual, 010, (2009) [4]. Allen J. Bard, Larry R. Faulkner, Electrochemical Methods: Fundamentals and Applications (2 nd ed), Wiley (2000) [5]. Cynthia G. Zoski, Handbook of Electrochemistry, Elsevier, B.V. (2006) 360