Basic Knowledge of Lithium Batteries - Second Part

 32.What is the IEC standard cycle life test?

 

IEC stipulates that the standard cycle life test for NiMH batteries is:

 

After the battery is discharged at 0.2C to 1.0V/piece

01) Charge at 0.1C for 16 hours, then discharge at 0.2C for 2 hours and 30 minutes (one cycle)

 

02) Charge at 0.25C for 3 hours and 10 minutes, discharge at 0.25C for 2 hours and 20 minutes (2-48 cycles)

 

03) Charge at 0.25C for 3 hours and 10 minutes, discharge at 0.25C to 1.0V (49th cycle)

 

04) Charge at 0.1C for 16 hours, leave for 1 hour, and discharge at 0.2C to 1.0V (50th cycle). For NiMH batteries, repeat 1-4 for a total of 400 cycles, and the 0.2C discharge time should be greater than 3 hours; for NiCd batteries, repeat 1-4 for a total of 500 cycles, and the 0.2C discharge time should be greater than 3 hours.

Basic Knowledge of Lithium Batteries - First Part

 I. Some important concepts

Lithium iron phosphate battery (LFP) and ternary lithium battery (NCM/NCA) are two mainstream lithium-ion battery technologies. The following are their main differences:

On the Technology and Market of Lithium-Ion Battery Electrolytes

Lithium-ion battery overview

Lithium-ion battery is a secondary battery. Its working principle is: during the charge and discharge process, lithium ions are in a state of movement from positive electrode → negative electrode → positive electrode. During the charge and discharge process, lithium ions are intercalated and deintercalated back and forth between the two electrodes. That is, during charging, lithium ions are deintercalated from the positive electrode and intercalated into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state. The opposite is true during discharge.

Lithium-ion batteries are complex systems consisting of positive electrode materials, negative electrode materials, electrolytes, separators, conductive agents, binders and packaging materials. Due to their high operating voltage, high specific energy density, long cycle life and wide operating temperature range, lithium-ion batteries have been widely used in new energy vehicles, energy storage and consumer electronics.

Electrolyte production and environment (a brief discussion)

1. Electrolyte

It is an important component of lithium batteries. It conducts lithium ions inside the battery and has an important impact on the performance and life of the battery. Lithium battery electrolyte is usually composed of organic solvents, electrolytes and additives.

 

Organic solvent is the main component of electrolyte, which is usually a flammable, explosive and toxic liquid, such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), etc. These organic solvents can dissolve electrolytes to form ion conductors, and can also provide a certain electrochemical stability.

 

Electrolyte is an ion conductor in the electrolyte, which is usually a lithium salt, such as LiPF6, LiBF4, LiClO4, etc. These lithium salts can dissociate into lithium ions and negative ions in the electrolyte, thereby realizing the conduction of lithium ions.

 

Additives are some chemical substances added to improve the performance of the electrolyte, such as conductive agents, film formers, corrosion inhibitors, etc. These additives can improve the conductivity, stability and corrosion resistance of the electrolyte, thereby improving the performance and life of the battery.

 

The performance of lithium battery electrolyte has an important impact on the performance and life of the battery. Therefore, factors such as electrochemical performance, stability, safety and cost need to be considered when designing and preparing the electrolyte. At the same time, the preparation and use of the electrolyte also need to strictly comply with relevant safety regulations and operating procedures to ensure the safety and reliability

Do you really understand electrolytes?

What is electrolyte?

The main materials of lithium-ion batteries are: positive electrode, negative electrode, electrolyte, and separator . As one of the four key materials of lithium-ion batteries, electrolyte is called the "blood" of lithium-ion batteries.

From the working principle of lithium ions, lithium-ion batteries are secondary batteries (rechargeable batteries) that mainly rely on the movement of lithium ions between the positive and negative electrodes to work. During the charging and discharging process, Li+ is embedded and de-embedded between the two electrodes: when charging, Li+ is de-embedded from the positive electrode and embedded in the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge.

Lithium battery-material-electrolyte related

 1. Composition of electrolyte

The basic functions of electrolyte:

It transfers lithium ions between the positive and negative electrodes, but insulates electrons to ensure that the battery can be charged and discharged smoothly.

Ideal electrolyte requirements:

1) It is an excellent conductor for lithium ions and an insulator for electrons;

2) Except for the migration of lithium ions, no other side reactions occur on the electrode surface;

3) Do not react with other battery components;

4) Good chemical stability; safe and environmentally friendly;

Lithium battery industry terms and explanations

 Lithium-ion battery: A battery that uses materials that can undergo lithium ion embedding/de-embedding reactions as positive and negative active materials, and uses organic electrolytes or polymer electrolytes containing lithium salts. It is a secondary battery (i.e., a rechargeable battery) that mainly relies on the movement of lithium ions between the positive and negative electrodes to work.