Battery Basic Knowledges

1. What is a battery?

A battery is an energy conversion and storage device that converts chemical or physical energy into electrical energy through a reaction. According to the different ways of converting energy, batteries can be divided into chemical batteries and physical batteries.

A chemical battery is a device that converts chemical energy into electrical energy. It consists of two chemical materials with different compositions to form the positive and negative electrodes, with an electrolyte as an intermediate medium. When a chemical battery is attached to an external carrier, it provides electrical energy by converting its internal chemical energy.

A physical battery is a device that converts physical energy into electrical energy.

2. What are the differences between primary batteries and secondary batteries?

The main difference is the difference in the active material. The active material of the secondary battery is reversible, while the active material of the primary battery is not reversible. The self-discharge of the primary battery is much smaller than that of the secondary battery, but the internal resistance is much larger than that of the secondary battery, so the load capacity is lower.

3. What is the electrochemical principle of NiMH battery?

The Ni-MH battery uses Ni oxide as the positive electrode, hydrogen storage metal as the negative electrode, and lye (mainly KOH) as the electrolyte. When charging the Ni-MH battery:

Positive reaction: Ni(OH)2 + OH- → NiOOH + H2O–e-

Negative reaction: M+H2O +e-→ MH+ OH-

When the NiMH battery is discharged:

Positive reaction: NiOOH + H2O + e- → Ni(OH)2 + OH-

Negative reaction: MH+ OH- →M+H2O +e-

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

The main component of the positive electrode of the lithium-ion battery is LiCoO2, and the negative electrode is mainly C. When charging,

Cathode reaction: LiCoO2 → Li1-xCoO2 + xLi+ + xe-

Negative reaction: C + xLi+ + xe- → CLix

Overall cell reaction: LiCoO2 + C → Li1-xCoO2 + CLix

The reverse reaction of the above reaction occurs during discharge.

5. What are the commonly used standards for batteries?

Commonly used IEC standards for batteries: The standard for nickel-metal hydride batteries is IEC61951-2:2003; the lithium-ion battery industry generally follows UL or specific national standards, such as Japan's JIS C standards for batteries.

IEC, the International Electrical Commission, is a worldwide organization for standardization composed of electrotechnical commissions of various countries. Its purpose is to promote the standardization of the world's electrical and electronic fields. IEC standards are standards developed by the International Electrotechnical Commission.

6. What are the main structural components of NiMH batteries?

The main components of NiMH battery are: positive electrode (nickel oxide), negative electrode (hydrogen storage alloy), electrolyte (mainly KOH), separator paper, sealing ring, positive cap, battery shell, etc.

7. What are the main structural components of lithium-ion batteries?

The main components of a lithium-ion battery are: battery upper and lower covers, positive electrode sheet (active material is lithium cobalt oxide), separator (a special composite film), negative electrode (active material is carbon), organic electrolyte, battery shell (divided into Steel shell and aluminum shell) and so on.

8. What is the internal resistance of the battery?

It refers to the resistance of the current flowing through the battery when the battery is working, and it is an important parameter to measure the performance of the battery. It consists of ohmic internal resistance and polarization internal resistance. The large internal resistance of the battery will cause the battery discharge working voltage to decrease and the discharge time to be shortened. The internal resistance is mainly affected by factors such as battery material, manufacturing process, and battery structure. Note: To measure the internal resistance of the battery, special internal resistance test equipment is required, not the ohm range of the multimeter.

9. What is the nominal voltage?

The nominal voltage of the battery refers to the voltage displayed during normal operation. The nominal voltage of the nickel-cadmium nickel-hydrogen battery is 1.2V; the nominal voltage of the lithium cobalt oxide battery is 3.6V, and the nominal voltage of the lithium iron phosphate battery is 3.2 V.

10. What is open circuit voltage?

Open circuit voltage refers to the potential difference between the positive and negative poles of the battery when the battery is not working (that is, when there is no current in the circuit). Through the open circuit voltage of the battery, the state of charge of the battery can be roughly judged

11. What is the working voltage?

The working voltage, also known as the terminal voltage, refers to the potential difference between the positive and negative electrodes of the battery in the working state (that is, when there is current in the circuit). In the battery discharge working state, when the current flows through the battery, it does not need to overcome the resistance caused by the internal resistance of the battery, so the working voltage is always lower than that of the open-circuit battery, and the opposite is true when charging.

12. What is a discharge platform?

Lithium batteries with different cathode materials have different characteristics, and generally take the most stable intermediate value in the discharge curve. Now take the ternary lithium battery as an example: the discharge platform is charged with constant voltage until the voltage is 4.2V and the current is less than 0.01C, and then the charging is stopped, then left for 10 minutes, and discharged to the remaining 50% capacity under the discharge current of 0.5C. static voltage. This is an important criterion for measuring the quality of the battery.

13. What is the (charge and discharge) rate? time rate?

The rate refers to the current value required by the battery to release its rated capacity within a specified time, which is equal to the multiple of the battery's rated capacity in terms of data value, usually represented by the letter C. For example, the nominal rated capacity of the battery is 1C (1 rate) for 600mAh, 0.5C for 300mAh, 10C for 6A (600mAh), and so on.

Hour rate refers to the number of hours it takes for a battery to discharge its rated capacity with a certain current. For example, the rated capacity of a lead-acid battery is 100Ah, and it takes 10 hours to discharge its rated capacity with a current of 10Ah. This is called the 10H hour rate, and so on.

14. What is the self-discharge rate?

Also known as charge retention capability, it refers to the retention capability of the battery stored in the battery under certain conditions when the battery is in an open circuit state, and is an important parameter to measure the battery performance. It is mainly affected by the battery manufacturing process, materials, storage conditions and other factors.

15. What is internal pressure?

Refers to the internal air pressure of the battery, which is caused by the accumulation of gas generated by the decomposition of moisture and organic solutions inside the battery during the charging and discharging process of the sealed battery. It is mainly affected by factors such as battery materials, manufacturing processes, and battery structure.

Continuous overcharge at high rate will cause the temperature of the battery to rise and the internal pressure to increase. In severe cases, it will have destructive effects on the performance and appearance of the battery, such as liquid leakage, drum bottom, increase in internal resistance of the battery, discharge time and cycle life. shorten etc.

Any form of overcharge of Li-ion will seriously damage the battery performance, or even explode, so Li-ion needs to use constant current and constant voltage charging during the charging process to avoid overcharging the battery.

16. Why does the battery need to be stored for a period of time before it can be packaged and shipped?

After a period of storage, the electrochemical performance of the internal components can be stabilized, and the self-discharge performance of the battery can be known while ensuring the quality of the battery. Of course, after the battery is stored for a certain period of time, the capacity and internal resistance of the battery are allowed to change to a certain extent.

17. Why should it be transformed into?

After the battery is manufactured, its internal positive and negative materials are activated by a certain charging and discharging method, and the process of improving the performance of the battery is called formation.

18. What is pairing?

During the manufacturing process of the battery, the actual capacity of the battery cannot be completely consistent due to technological reasons. It is detected through certain charging and discharging conditions, and the process of classifying the battery by capacity is called capacity pairing.

19. What is the rated capacity of the battery?

The rated capacity of the battery refers to the design and manufacture of the battery that stipulates or guarantees that the battery should theoretically release the minimum amount of electricity under certain discharge conditions. Common units of capacity are: mAh, Ah (1Ah=1000mAh).

20. What is the actual capacity of the battery?

The actual capacity of the battery refers to the actual power released by a fully charged battery under certain discharge conditions, which is mainly affected by the discharge rate and temperature (strictly speaking, the actual capacity of the battery should specify the charge and discharge conditions).

21. What is static resistance?

That is, the internal resistance of the battery at rest.

22. What is dynamic resistance?

That is, the internal resistance of the battery during charging and discharging.

23. What is the load capacity of the battery?

When the positive and negative ends of the battery are connected to the electrical appliance, the output power when it can work normally is the load capacity of the battery.

24. What is the charging efficiency?

Charging efficiency refers to the ratio of the power consumed by the battery to the rated capacity during the charging process. This parameter is mainly affected by the battery process, formula and the working environment temperature of the battery. The higher the ambient temperature, the lower the charging efficiency.

25. What is discharge efficiency?

Charging efficiency refers to the ratio of the amount of electricity released by a battery during discharge to its rated capacity. This parameter is mainly affected by the battery process, formula and the working environment temperature of the battery. The higher the discharge rate, the lower the discharge efficiency. The lower the temperature, the lower the discharge efficiency.

26. What is the difference between the various rechargeable batteries that are common today?

At present, nickel-cadmium, nickel-hydrogen and lithium-ion rechargeable batteries are widely used in various portable electrical devices (such as notebook computers, video cameras and mobile phones, etc.), and each rechargeable battery has its own unique chemical properties.

The main difference between NiCd and NiMH batteries is that NiMH batteries have a higher energy density. Compared with the same type of battery, the capacity of NiMH battery is twice that of NiCd battery. This means that the use of NiMH batteries can greatly extend the working time of the equipment without adding extra weight to the electrical equipment. Another advantage of NiMH batteries is that: A greatly reduces the problem of "memory effect" that exists in cadmium batteries, thus making NiMH batteries more convenient to use. NiMH batteries are more environmentally friendly than NiCd batteries because there are no toxic heavy metal elements inside.

Li-ion has also quickly become the standard power source for portable devices. Li-ion can provide the same energy as NiMH batteries but about 35% less weight, which is critical for consumer electronics devices. of. Li-ion's complete lack of "memory effect" and the absence of toxic substances are also important factors that make it a standard power supply.

27. What is the memory effect?

The battery memory effect refers to the phenomenon that the battery is not fully charged and discharged for a long time, as if the user's daily charging and discharging range and pattern are memorized, which eventually reduces the battery capacity. Generally, it only happens in less NiCd/NiMH batteries. Lithium-ion batteries do not have this effect.

28. How to eliminate the memory effect of the battery

The normal maintenance is to perform deep discharge on a regular basis. On average, perform a deep discharge (discharge to 1.0V/cell) every month (or 30 cycles) of use. In normal use, try to use light capacity and other means to alleviate the formation of memory effect.

For batteries that have not undergone regular deep discharge for a long time, due to the accumulation of memory effect, capacity recovery cannot be performed in the form of regular deep discharge. At this time, professional equipment is required for maintenance.

29. Comparison of technical parameters of Ni, Cd, NiMH and Li-ion.

Note: The charging rate is 1C

30. What are the "green batteries" currently in use and research?

Green battery refers to a type of high-performance, pollution-free battery that has been put into use or is being developed in recent years. At present, lithium-ion batteries, metal hydride nickel batteries, mercury-free alkaline zinc-manganese batteries that are being widely used, and lithium or lithium-ion plastic batteries, combustion batteries, and electrochemical energy storage supercapacitors that are being developed are all new types of batteries. The category of green battery.

In addition, the concept also includes solar cells that utilize solar energy for photoelectric conversion.

31. What battery will dominate the battery market?

As cameras, mobile phones, notebook computers, multimedia devices, electronic cigarettes, balance cars and other consumer electronic products occupy an increasingly important position in people's lives, compared with primary batteries, secondary batteries are rechargeable batteries. A large number of applications in these fields. The rechargeable battery will develop in the direction of small size, light weight, capacity and intelligence.

32. What is a lithium-ion battery?

It refers to rechargeable batteries that use lithium ions as reactive materials, including lithium cobalt oxide batteries, lithium carbonate batteries, lithium iron phosphate batteries, and ternary lithium batteries.

33. How does a lithium-ion battery work?

During discharge, lithium in the phase intercalation compound of lithium and carbon dissolves from the negative electrode to form lithium ions into the electrolyte, passes through the electrolyte and intercalates in the positive electrode crystal to form an intercalation compound. During charging, the lithium ions intercalated at the positive electrode return to the electrolyte, and then form intercalation compounds with carbon on the negative electrode, and the cycle starts over and over again.

34. What are the advantages of lithium-ion batteries compared with nickel/cadmium, nickel/hydrogen, and lead-acid batteries?

High specific energy, low self-discharge rate, good high and low temperature performance and long charge and discharge life.

35. What is the average voltage of the battery?

The average value of the voltage from the beginning to the end of the discharge when the battery is discharged.

36. What is the energy density of the battery?

Refers to the electric energy contained in the unit volume of the battery. This is an important indicator to judge the performance of a certain material system or product.

37. What is the operating temperature range of lithium-ion batteries?

Generally speaking, lithium batteries are charged (-10-45°C) and discharged (-30-55°C).

38. What are the characteristics of the lithium-ion battery type related to the battery?

The shape of the battery is length, width, height and the capacity of the battery.

39. What are the two most important factors that affect the cycle performance of lithium-ion batteries?

The nature of the active material and the type and content of impurities.

40. How to control the moisture inside the battery during the production process?

1. Do a good job of moisture-proof and moisture-proof treatment.

2. Shorten the operation time and reduce the exposure time of the pole piece in the air.

3. Carry out the baking operation reasonably and correctly.

4. Try to work in a dry environment.

41. What is the active cathode material of lithium ion battery?

Lithium salts; such as lithium cobaltate, lithium manganate, lithium nickelate, etc.

42. What is the active negative electrode material of lithium ion battery?

Graphite powder

43. Why should a conductive agent be added to the electrode material?

When the battery is working, the active material of the battery will not dissolve in the electrolyte regardless of charging and discharging. In order to strengthen the conductivity of the active material with the grid and the current collector, a conductive agent is added and discharged.

44. What is the composition of the electrolyte of lithium ion battery?

Commonly used are lithium hexafluorophosphate, lithium tetrafluorophosphate (LiPF6, LiClO4) and so on.

45. What is the purpose of ingredients in the battery cell production process?

The active material is dispersed evenly, which is convenient for pulling the pulp evenly and the sizing amount is constant.

46. The three basic parameters of the positive and negative electrode sheets.

Pulp temperature, speed, coating amount.

47. How to control the coating amount of the pole piece?

According to the solid content and specific gravity of the positive and negative slurries, adjust the gap between the head and the cutter of the pulping machine, and control the thickness of the pulping to achieve control.

48. How to judge the quality of the pole piece during the pulping process.

The surface of the pole piece is flat, smooth, the coating is uniform, the adhesion is good, dry, and the pole piece is good, and the pole piece has no defects. Bad pole piece.

49. The main precautions for the positive and negative plates of the cell.

1. Check the knife edge for burrs and unevenness, and pay attention to the safety of the knife during operation.

2. The positive and negative cutting knives cannot be mixed.

3. Check the quality of the pole pieces at any time during the cutting process, separate the unqualified grades, and do not mix them up.

4. After the cut pieces are checked, they will be transferred to the next process operation.

50. What is the purpose of the positive and negative positive stoving?

Remove the water and organic solvent in the pole piece.

51. What kind of tabs are used for the positive electrode?

Use aluminum tabs.

52. What kind of tabs are used for the negative electrode?

Nickel strap tabs are used.

53. What effect does the humidity in the winding workshop have on the battery quality?

When the humidity in the winding room is high, the pole piece absorbs a large amount of water, which increases the moisture content of the pole piece, resulting in an increase in the internal gas and the increase in the internal pressure of the battery, which endangers the safety performance of the battery. The increase of water content consumes more active material in the battery, which reduces the battery capacity. The lower the humidity, the more reliable the cell manufacturing process.

54. Can the floor be wiped with water in the winding workshop?

Negative

55. What inspections need to be done before the battery cap is used?

Inspection of external dimensions, shape, thickness, insulation, sealing, corrosion resistance, material holding and other items.

56. How to prevent battery leakage?

To prevent battery leakage, the following aspects should be done:

1. When welding the battery shell and the cap, the welding should be firm and sealed, and there should be no leakage welding, virtual welding, and no cracks or cracks in the welding seam.

2. When the steel ball is sealed, the size of the steel ball is appropriate, and the material of the steel ball is the same as that of the cap. Welding is free of cracks, cracks and the welding is firm.

3. The positive pole of the cap is tightly connected without gaps, and the insulating gasket has proper elasticity, is corrosion-resistant and not easy to age.

57. What treatments need to be done before the battery is injected?

Glued and vacuum baked.

58. What is the effect of conductivity on the working current of the battery?

Conductivity affects the rate discharge rate, and the internal resistance of the battery, and the voltage of the battery.

59. What factors affect the internal resistance of the battery?

The conductivity of the electrolyte, the performance of the battery shell material, the conductivity of the pole piece and the cross-sectional area of the tab material. The quality of battery welding.

60. What factors affect the capacity of the battery?

Characteristic properties of positive and negative materials, as well as the type and the amount of active materials.

-Correct ratio of positive and negative active materials.

-The concentration and type of electrolyte.

-production process.