March 14, 2024
Analysis of lithium battery voltage and its influencing factors
As an important energy supplier for modern electronic devices, lithium batteries are widely used in products such as mobile phones, laptops, and electric vehicles. Understanding lithium battery voltage and its influencing factors is crucial for improving battery efficiency and extending its healthy lifespan.
This article will start from the basic working principles of lithium batteries, exploring the differences in lithium battery voltage among different materials, the voltage changes during charge and discharge processes, and their impact on battery performance.
Table of Contents
Add a header to begin generating the table of contents
Basic working principle of lithium-ion batteries
The storage and release of electrical energy in lithium-ion batteries mainly rely on the movement of lithium ions between the positive and negative electrodes. During charging, an external power source provides energy, causing lithium ions to move from the lithium metal oxide material at the positive electrode to the negative electrode (such as graphite) for storage.
During discharge, lithium ions move back from the negative electrode to the positive electrode, releasing energy for device use. The lithium battery voltage changes involved in this process are crucial.
Differences in voltage among different materials of lithium batteries
Differences in electrode potential
The formation of lithium battery voltage is primarily influenced by the electrode potential of the lithium battery. The positive electrode materials often consist of different types of lithium metal oxides, while the negative electrode materials are mostly graphite or other carbon-based materials.
Due to the different potentials of these materials in redox reactions, the operating voltage of lithium batteries varies. Common types of lithium-ion batteries include lithium iron phosphate batteries, ternary lithium batteries, and lithium cobalt oxide batteries.
Differences in material types
There are significant differences in the nominal voltages of different types of lithium batteries. For example, the nominal voltage of lithium iron phosphate batteries is approximately 3.2V, while the nominal voltage of ternary lithium batteries and lithium cobalt oxide batteries is about 3.7V. This difference primarily arises from the different positive electrode materials, as the electrochemical reaction characteristics of different materials directly affect voltage.
Influence of electrolytes
Although different types of lithium batteries commonly use lithium salt electrolytes, the deposition and behavior of these electrolytes in the battery change with variations in the positive and negative electrode materials.
The properties of the electrolyte influence the migration speed of lithium ions and the performance of battery voltage. Therefore, when considering product purchases, attention should be paid to parameters such as the battery’s nominal voltage, capacity, size, and other specifications.
Voltage changes during charging and discharging
During the charging and discharging processes of lithium-ion batteries, the lithium battery voltage undergoes significant changes. These changes are closely related to the battery’s internal chemical reactions and physical characteristics.
Lithium battery voltage changes during charging
In the initial phase of charging, the lithium battery voltage is usually low, and as the internal chemical reactions of the battery gradually reach equilibrium, the voltage rises. Taking ternary lithium batteries as an example, the charging process can generally be divided into the following stages:
- Trickle Charging Stage: When the lithium battery voltage is below 3V, pre-charging occurs with the current set to 1/10 of the maximum charging current, and the voltage rises slowly.
- Constant Current Charging Stage: Once the voltage exceeds the trickle charging threshold, the battery enters the constant current charging phase, the current increases, and the voltage continues to rise, reaching the set level of 3.0–4.2V.
- Constant Voltage Charging Stage: When the lithium battery voltage reaches 4.2V, charging enters a constant voltage state, maintaining this voltage while the current gradually decreases over time until charging is complete.
Voltage changes during discharging
When discharging, the trend of voltage change in lithium-ion batteries is the opposite of charging. The voltage is relatively high at the beginning of discharge, and then, as lithium ions are consumed, the voltage gradually decreases. When the battery load approaches depletion, the voltage drops sharply. The discharge process can also be divided into three stages:
- Rapid Decline Stage: In the initial phase, the voltage decreases rapidly; the greater the discharge rate, the faster the decrease.
- Platform Region: The lithium battery voltage remains relatively stable within a certain range; under smaller discharge rates, the platform region lasts longer, exhibiting higher voltage.
- Sharp Decline Stage: As discharge cutoff approaches, the voltage will sharply drop to the set cutoff voltage.
Causes of voltage changes
The reasons for voltage changes in lithium batteries are multifaceted, primarily including the following points:
- Internal Resistance: The battery experiences internal resistance during charge and discharge, causing the voltage to decrease.
- Polarization Effects: During charge and discharge, uneven charge distribution on the electrode surface can lead to voltage fluctuations.
- Chemical Reaction Kinetics: The reaction rates of chemical processes within the battery directly affect how quickly the voltage changes.
The impact of voltage changes on lithium-ion battery performance
Relationship between voltage and capacity
Generally, battery capacity is directly proportional to voltage. A higher lithium battery voltage means the battery can store more energy, leading to longer usage times. Therefore, high-voltage lithium batteries are often considered superior choices.
Relationship between voltage and discharge curve
The discharge curve reflects how lithium battery voltage changes over time during use. Different voltages can alter the shape and slope of the discharge curve; a smooth declining trend is the expected behavior of the battery. Dramatic voltage changes can directly affect the normal operation of electronic devices.
Relationship between voltage and charge/discharge speed
Higher voltage allows lithium-ion batteries to charge and discharge more quickly. This characteristic is particularly important for devices that require rapid charging. However, controlling high voltage is necessary to prevent overheating or damage.
Relationship between voltage and safety
Overcharging and over-discharging behaviors can affect lithium-ion battery safety, potentially leading to severe consequences such as fires. Therefore, when designing charging circuits, the voltage limits of the batteries should be considered to ensure safety. When the battery voltage exceeds the normal range, power cutoff or short-circuit protection measures should be implemented.
Other effects of voltage changes
Lithium batteries that remain in a low-voltage state for a long time may accelerate internal harmful chemical reactions, such as battery electrolyte decomposition, leading to irreversible capacity loss. Changes in the microscopic structure of the battery may also accelerate aging and performance degradation.
Conclusion
The lithium battery voltage experiences significant fluctuations during charge and discharge, influenced by various factors, including the differences in nominal voltage among different materials, voltage fluctuations during charge and discharge processes, and the impact of voltage changes on battery performance.
Understanding the relevant characteristics of lithium battery voltage will aid in the proper configuration of power systems, ensuring efficient and safe operation of devices. For future battery development and applications, research and practices that utilize new materials and technologies to indirectly regulate battery voltage and improve performance will undoubtedly promote further advancements in lithium battery technology.
Who we are
Tycorun, a prominent player in the battery-swapping industry, specializes in developing and manufacturing battery swap station and lithium-ion batteries. The company aims to offer sustainable energy solutions for electric vehicles.
Tycorun has made significant inroads into the Chinese market, primarily targeting urban regions where the need for electric two-wheelers is substantial. The company consistently allocates resources to research and development to improve its battery technology and broaden its network of swapping stations.
The battery swapping stations created by Tycorun are both user-friendly and efficient. Their lithium-ion batteries are renowned for their high energy density and long-lasting performance, suitable for different models of electric two-wheelers. Additionally, Tycorun offers comprehensive software solutions for monitoring and managing our batteries.
Related post
October 2, 2023
September 19, 2023
Willow
Willow is a materials engineer with a Master’s degree in Materials Science and Engineering, specializing in lithium-ion battery materials and energy storage technologies.
Her work focuses on EV battery swapping solutions, battery innovation, and new energy industry trends, aiming to translate research insights into practical applications for sustainable transportation.
Leave a comment