Basic Knowledge of Battery

1. What is a battery?

A battery is a device for energy conversion and storage, which converts chemical or physical energy into electrical energy through a reaction.A battery is a chemical power source, consisting of two electrochemically active electrodes of different components, the two electrodes are immersed in an electrolyte that can provide ion conduction.When connected to an external electronic carrier, it provides energy to the outside by converting its internal chemical energy into electrical energy.

2. Polymer lithium ion battery?

he so-called polymer lithium ion battery means that at least one of the three main battery structures uses polymer materials as the main battery system. In the polymer lithium-ion battery system currently being developed, polymer materials are mainly used in positive electrodes and electrolytes.The positive electrode material includes conductive polymer or inorganic compounds commonly used in lithium ion batteries, the electrolyte can use solid or colloidal polymer electrolytes, or organic electrolytes, and the negative electrode usually uses lithium metal or lithium-carbon intercalation compounds. Generally, lithium-ion technology uses liquid or colloidal electrolytes, so strong secondary packaging is required to contain combustible active ingredients, which increases weight and cost, and also limits size flexibility. There is no excess electrolyte in the polymer lithium ion process, so it is more stable, and it is not easy to cause dangerous situations due to battery overcharging, needle sticks, collisions or other damage, and overuse.

The new generation of polymer lithium-ion batteries can be thinner (the thinnest 0.5 mm), any area and any shape in shape, which greatly improves the flexibility of battery shape design, so that it can be made to meet product needs. Batteries of any shape and capacity provide application equipment developers with a high degree of design flexibility and adaptability in power solutions to maximize their product performance.At the same time, the unit energy of polymer lithium ion battery is 50% higher than the current general lithium ion battery, and its capacity, charge and discharge characteristics, safety, working temperature range, cycle life (more than 500 times) and environmental performance are greatly improved than lithium ion battery.

3. What are the similarities and differences between primary batteries and secondary batteries?

The primary battery can only be discharged once, and the secondary battery can be repeatedly charged and discharged. The rechargeable battery undergoes a reversible change in the volume and structure of the electrode during discharge. Generally speaking, the mass specific capacity and volume specific capacity of primary batteries are larger than those of general rechargeable batteries, but the internal resistance is much larger than that of secondary batteries, so the load capacity is lower.

4. What is the electrochemical principle of lithium ion batteries?

The main component of the positive electrode of lithium ion batteries is LiCoO2, and the negative electrode is mainly C. Positive reaction during charging: LiCoO2→ Li1-xCoO2 + xLi+ + xe- Negative reaction: C + xLi+ + xe- CLix Total battery reaction: LiCoO2 + C →Li1-xCoO2 + CLix The reverse reaction of the above reaction occurs during discharge.

5. What is the main structure of the battery?

The main components of the battery are: positive electrode sheet, negative electrode sheet, separator film, and insulating packaging layer.

6. What are the components of a mobile phone lithium battery and what are the functions of each part?

The mobile phone lithium battery is mainly composed of the upper and lower covers of the plastic shell, the lithium battery core protection circuit board (PCB), and the battery core. The functions of each part are as follows: Cell: Provides rechargeable power supply. Protect the circuit board: prevent the battery from being overcharged and short-circuited.

7. What are the main aspects of secondary battery performance?

Mainly include voltage, internal resistance, capacity, self-discharge rate, cycle life, sealing performance, safety performance, storage performance, appearance, etc. There are also overcharge, overdischarge, solderability, corrosion resistance, etc.

8. What are the electrical performance indicators of conventional battery cell and how to measure them?

There are many electrical performance indicators of the battery cell. Here, only the most important electrical characteristics are introduced:

A. Battery cell capacity: This indicator reflects the amount of electric energy that the battery cell can store in milliampere hours. For example, 1600mAh means that the battery can be discharged continuously for one hour at 1600mA.

B. Battery cell life: This indicator reflects the number of repeated charge and discharge cycles of the battery cell.

C. Internal resistance of the battery cell: As mentioned above, the internal resistance of the battery cellis as small as possible, but it cannot be zero.

D. Battery cell charging upper limit protection performance: When the lithium battery is charged, its voltage upper limit has a rated value (nominal 4.2V). In any case, the voltage of the lithium battery is not allowed to exceed this rating. It is set and guaranteed by the IC selected on the PCB board.

E. Battery cell discharge lower limit protection performance: When the lithium battery cell is discharged, the voltage of the lithium battery is not allowed to be lower than a certain rated value (nominal 0.75V) under any circumstances, and the rated value is determined by the IC selected on the PCB board. Set up and guarantee.

F. It should be noted that when the general battery cell in the mobile phone is discharged, the mobile phone shuts down due to insufficient battery power before reaching the lower limit protection value.

G. Battery cell short-circuit protection feature: When the exposed positive and negative plates of the lithium battery cell are short-circuited, the IC on the PCB board should immediately turn off the MOSFET. When the short-circuit fault is eliminated, the battery cell can immediately output electrical energy. These are identified and executed by the IC on the PCB.

9. What are the routine safety test items for batteries?

1. Internal short circuit test 2. Continuous charge test 3. Overcharge test 4. High current charge test 5. Forced discharge test 6. Drop test 7. Drop test from a height 8. Penetration test 9. Squeeze test.

10. What is the rated capacity and actual capacity of the battery?

1. Rated capacity: refers to the amount of electricity released when the battery is discharged to the cut-off voltage under certain charging and discharging conditions.

2. Actual capacity: refers to the minimum amount of electricity that the battery should discharge under certain discharge conditions when designing and manufacturing the battery. The actual capacity is always lower than the theoretical capacity. (We discharge to 2.75 V with 0.2C A current according to the inspection and arbitration charging system stipulated in the national standard).

In order to compare with other batteries in parallel, we introduced the concept of specific capacity, which refers to the capacity of the battery per unit mass or unit volume, called mass specific capacity and volume specific capacity.

11. What are the common charging methods for batteries?

1. Constant current charging: the charging current is a certain value during the whole charging process.

2. Constant voltage charging: During the charging process, both ends of the charging power supply maintain a constant value, and the current in the circuit gradually decreases as the battery voltage increases.

3. Constant current and constant voltage charging: The battery is first charged with a constant current. When the battery voltage rises to a certain value, the voltage remains unchanged, and the current in the circuit gradually drops to a small amount, eventually tending to zero.

4. The most commonly used charging method for lithium batteries: constant current and constant voltage charging.

12. What is charging efficiency?

Refers to the ratio of the discharged capacity to the input battery capacity when the battery is discharged to a certain cut-off voltage under certain discharge conditions.

It can be calculated according to the following formula: charging efficiency = (discharging current * discharge time to cut-off voltage / charging current * charging time) * 100%.

The input energy is used to convert the active material into a charged state. The charging efficiency is affected by the charging rate and the ambient temperature. The charging current must be within a certain range during charging. If the current is too small or too large, the charging efficiency is very low.

13. What is the self-discharge of the secondary battery and what is the self-discharge rate of the polymer lithium battery?

Self-discharge is also called charge retention capability, which refers to the retention capability of the stored power of the battery under certain environmental conditions in an open circuit state. After the battery is fully charged and left open for a period of time, a certain degree of self-discharge is normal. The monthly self-discharge rate of polymer lithium battery is less than 5%.

14. What is the internal resistance of the battery and how to measure it?

The internal resistance of the battery refers to the resistance that the current flows through the battery when the battery is working, and is generally divided into AC internal resistance and DC internal resistance.Since the internal resistance of the rechargeable battery is very small, the actual value of the internal resistance cannot be measured due to the polarization of the electrode capacity when measuring the DC internal resistance. And measuring the AC internal resistance can avoid the influence of the polarization internal resistance to get the true internal resistance value.

15. What is the standard overcharge resistance test?

IEC stipulates that the standard overcharge test for lithium batteries is as follows: 1) Discharge the battery at 0.2C to 3.0 V.

2). Use the current I to set a voltage of 10V arbitrarily to charge the battery, and the charging time is T=2.5*C5/I.

3). The battery will not explode and catch fire eventually.

16. What is a short circuit test?

Connect the fully charged battery directly to the positive and negative poles with a wire in the explosion-proof box. The battery should not explode or catch fire.

17. What is a drop test?

After fully charging the battery pack, drop it from three different directions at a height of 1m onto the hard rubber plate. Do it twice in each direction. The battery pack's electrical performance should be normal and the outer packaging should not be damaged.

18. What is a vibration experiment?

The battery vibration test method is: the battery is discharged at 0.2C to 3.0V and then charged at 1C, charged to 4.2V with constant current and constant voltage, cut-off current is 10mA, and placed for 24 hours and then vibrated under the following conditions:

The amplitude is 0.8mm, making the battery vibrate between 10HZ-55HZ, increasing or decreasing at a vibration rate of 1HZ per minute, the battery voltage change should be between +/-0.02V, and the internal resistance change within 5m.

19.What is an impact test?

After the battery is fully charged, place a 15.8mm diameter hard rod horizontally on the battery, drop a 20-pound weight from a height of 610mm, and hit the hard rod. The battery should not explode, catch fire or leak liquid.

20. What is a penetration experiment?

After the battery is fully charged, use a nail with a diameter of 2.5mm-5mm through the center of the battery and leave the nail in the battery. The battery should not explode and catch fire.

21. What are the precautions when using the battery?

1)Read the battery manual carefully and use the recommended battery;

2)Check whether the contacts of electrical appliances and batteries are clean, wipe them with a damp cloth if necessary, and install them in the correct polarity after drying;

3)Do not allow children to replace the battery without adult supervision. Small batteries such as AAA should be placed out of the reach of children.

4)Do not mix new and old batteries or different types of batteries

5)Don't try to regenerate the primary battery by heating, charging or other methods

6)Do not short-circuit the battery

7)Do not heat the battery or throw the battery into water

8)Do not disassemble the battery

9)Turn off the switch after using the electrical appliance

10)The battery should be taken out of electrical appliances that have not been used for a long time

11)The battery should be stored in a cool, dry place without direct sunlight.

22. What impact does the battery have on the environment?

Almo

st all batteries today do not contain mercury, but heavy metals are still an essential part of mercury batteries, rechargeable nickel-cadmium batteries, and lead-acid batteries. If improperly handled and in large quantities, th, e heavy metals will have a harmful effect on the environment. At present, there are already specialized agencies in the world to recycle manganese oxide nickel cadmium and lead-acid batteries. For example, the non-profit organization RBRC company https://www.rbrc.com. Polymer batteries have won the reputation of being green and environmentally friendly with no liquid, zero discharge, and no heavy metals. It is an ideal energy product for an environmentally friendly society in the future.

23. n