Views: 211 Author: Ubest Publish Time: 2023-10-30 Origin: Site
The resistance encountered by the current passing through the inside of the lithium battery during discharge or charging is referred to as internal resistance. The conductivity of the material inside the battery, the ion transport rate of the electrolyte, the contact resistance between the electrode and the electrolyte, and many other factors all contribute to this. The size of the internal resistance has a direct impact on lithium battery performance, including output power, cycle life, temperature characteristics, and so on.
A. One of the limiting factors for lithium battery output power is internal resistance. When the internal resistance of the battery is high, the current passing through it causes a large voltage drop, resulting in a decrease in the battery's output power.
B. Internal resistance will cause the battery to self-discharge. Because of the presence of resistance within the battery, the battery will have a certain current flow when not in use, resulting in self-discharge.
C. The internal resistance of the battery influences its temperature characteristics. Batteries with a high internal resistance generate more heat during discharge or charging, raising the battery temperature and reducing battery performance. Click here for 700W 537Wh Portable Power Station with Lithium Battery.
In practical applications, DC internal resistance is frequently used to assess the health of lithium batteries, predict life, and estimate the battery's SOC (State of Charge) and SOP (State of Power). By measuring the battery's DC internal resistance, information about the battery's status can be obtained, providing a foundation for battery management and control and further improving the battery's efficiency and life, as shown below:
A lithium battery's health is determined by how much it degrades while being used; this is typically determined by looking at the rate at which internal resistance rises and the capacity decays. Because the change in DC internal resistance can reflect physical and chemical changes inside the battery, it can be used to assess the battery's health. When a battery's health deteriorates, its internal resistance rises.
A battery's SOC refers to its current state of charge, which is the ratio of the remaining available energy in the battery to the total energy. The DC internal resistance and the battery's state of charge (SOC) have a relationship. The SOC of a battery can be estimated by measuring its DC internal resistance. The SOC of the battery can be calculated using the existing internal resistance-charge state relationship model by measuring the battery's DC internal resistance.
DC internal resistance is important in lithium battery health evaluation, life prediction, and estimation of SOC and SOP.
Internal resistance measurement methods are broadly classified as static measurement and dynamic measurement.
The static measurement method calculates the battery's internal resistance by measuring the difference between the open circuit voltage and the short circuit current. The following are the specific steps:
(1) Leave the battery for a while to allow the electrochemical reaction within it to balance.
(2) Determine the battery's open circuit voltage.
(3) Connect a load between the battery's positive and negative terminals to measure the short-circuit current.
(4) Calculate the internal resistance of the battery using Ohm's law.
The dynamic measurement method involves using an AC electrical signal to measure the internal resistance of the battery. The following are the specific steps:
(1) Connect the battery's positive and negative terminals with an alternating current electrical signal.
(2) Determine the battery's current and voltage signals.
(3) Determine the battery's internal resistance using the phase difference and amplitude ratio of the current and voltage signals.
Many factors influence the size of the internal resistance, the most important of which are as follows:
1. The battery material's conductivity The rate at which current is transmitted inside the battery is determined by the conductivity of the battery material. The lower the internal resistance, the higher the conductivity of the material inside the battery.
2. The electrolyte's ion transport rate has a direct impact on the battery's internal resistance. The lower the internal resistance, the faster the ion transport rate in the electrolyte.
3. Resistance to contact between the electrode and the electrolyte Internal resistance is also affected by the contact resistance between the electrode and the electrolyte. The lower the internal resistance, the lower the contact resistance.
4. The battery's structural design The internal resistance of a battery is also affected by its structural design. For example, the larger the battery's electrode area, the lower the internal resistance.
5. Temperature Temperature has a significant impact on internal resistance. In general, the lower the internal resistance, the higher the temperature.
Some steps must be taken to reduce internal resistance in lithium batteries to improve their performance. Here are some common approaches:
1. Improve the battery material Improve the conductivity of the battery material by changing its composition and structure, thereby lowering internal resistance.
2. Optimize the electrolyte to change its composition and concentration and improve the transmission rate of ions in the electrolyte, lowering internal resistance.
3. Improve the contact between the electrode and the electrolyte by changing the contact mode, lowering the contact resistance between the electrode and the electrolyte, and thus lowering the internal resistance.
4. Improve the structural design of the battery Increase the area of the electrode by changing the structural design of the battery, reducing internal resistance.
5. Manage the temperature Control the battery's operating temperature properly to avoid overheating and to reduce internal resistance.
Internal resistance is an important index in evaluating the performance of lithium batteries because it directly affects the battery's output power, cycle life, and temperature characteristics. The internal resistance of the battery can be reduced and the performance of the lithium battery can be improved using reasonable measurement methods and optimization measures. The internal resistance of lithium batteries is expected to decrease further as science and technology advance, providing better support for the development of lithium battery applications.