Lithium ion batteries are widely used in consumer electronics and new energy vehicles. Ternary lithium batteries have attracted much attention due to their high energy density and good performance. In actual use, battery life has become the core issue that users and manufacturers are concerned about. This article will focus on the life of ternary lithium battery, and analyze its definition, influencing factors, manifestation forms and common methods of extending its life in detail to help readers fully understand the life characteristics of ternary lithium battery.

I. Basic concept of life of ternary lithium battery

ternary lithium battery life usually refers to the time or number of cycles that the battery can continue to use under the condition of meeting certain performance indicators. Specifically, battery life can be divided into two forms:

1. cycle Life: refers to the number of battery charge and discharge cycles until the battery capacity decays below 80% of the initial capacity. This indicator reflects the durability of the battery during repeated use.

2. Calendar life: refers to the process that the capacity and performance of the battery gradually decrease with the passage of time when it is stored or idle. Calendar life is mainly affected by temperature and battery status (such as charging status).

The service life of ternary lithium battery directly affects the service experience and economic benefits of the equipment, so it is of great significance for product design, user use and maintenance to accurately understand and evaluate the service life.

II. Main factors affecting the life of ternary lithium batteries

the life of ternary lithium battery is affected by many internal and external factors, including material characteristics, service environment, charging and discharging conditions and maintenance methods.

1. Characteristics of positive and negative electrode materials

the cathode materials of ternary lithium batteries are generally nickel cobalt manganese (NCM) or nickel cobalt aluminum (NCA) oxide, which have the advantages of high capacity and high voltage, but are relatively prone to structural changes and material aging, the cycle stability of the battery is affected. The negative electrode is mostly graphite, and problems such as expansion and crack may occur in the charging and discharging process of graphite, resulting in the attenuation of battery capacity.

2. Depth of charge and Discharge (Depth of Discharge,DoD)

the depth of charge and discharge refers to the capacity ratio released by the battery in each cycle. Deep discharge (such as discharge to nearly 0%) will aggravate the chemical and mechanical stress of the battery and shorten the cycle life. On the contrary, shallow charge and shallow discharge can effectively prolong the service life of the battery.

3. Charge and discharge rate

fast ChargeAnd large current discharge will cause the internal temperature of the battery to rise, and the deterioration of electrode materials and electrolyte will accelerate, thus affecting the battery life. The effect of high rate charge and discharge on the life of ternary lithium battery is particularly obvious.

4. Working temperature

temperature is the key environmental factor affecting the life of ternary lithium battery. High temperature environment will accelerate electrolyte decomposition and electrode material aging, while low temperature will reduce battery activity, resulting in temporary capacity decline. Long-term high-temperature storage or use will seriously shorten the battery life.

5. State of Charge (SoC)

keeping the battery in a high voltage state (high SoC) or a low voltage state (low SoC) for a long time will damage the battery life. Medium Battery range is friendly to battery life.

6. Battery management system (BMS)

by monitoring the battery status, adjusting the charge and discharge parameters to prevent extreme conditions such as overcharge, overdischarge, and overheating, BMS plays a key role in prolonging the battery life.

III. Expression form and attenuation process of ternary lithium battery life

with the increase of usage time and cycle times, ternary lithium battery will experience two major changes: capacity attenuation and internal resistance increase.

1. Capacity attenuation

capacity attenuation shows that the amount of charge that the battery can store and release gradually decreases, resulting in a decrease in endurance. Generally speaking, after reaching 500-1000 cycles, the capacity of ternary lithium battery will drop to about 80% of the original capacity, which is usually regarded as the end of battery life.

The main reasons of capacity attenuation include structural damage of electrode materials, irreversible loss of lithium ions and decomposition of electrolyte, etc.

2. Increase of internal resistance

the increase of internal resistance shows that the voltage drop increases when the battery is discharged, which leads to the weakening of the battery power output capability. The increase of internal resistance not only affects the performance, but also causes heat, further accelerating the deterioration of the battery.

3. Security performance changes

with the increase of life, the internal decomposition products of the battery increase, and the stability of the electrode material decreases, which may increase the risk of thermal runaway. Therefore, the safety at the end of battery life is also an important concern.

IV. Effective methods to prolong the life of ternary lithium batteries

according to various factors affecting battery life, reasonable measures can effectively prolong the service life of ternary lithium battery.

1. Reasonable charging and discharging strategy

avoid over-discharge and over-charging, keep the battery power between 20% and 80%; Reduce the number of deep cycles; Avoid frequent fast charging and reasonably control the charging current.

2. Optimize the working temperature

try to avoid the battery running and storage in high temperature environment, and take battery thermal management measures to ensure that the battery temperature is stable in the appropriate range (generally 15-35 ℃). When the temperature is low in winter, the preheating system can be used to increase the battery temperature.

3. Adopt advanced battery management system

monitor the voltage, current, temperature and State of the battery in real time through the BMS, adjust the charging and discharging parameters in time to avoid the battery working in extreme state, thus protecting the battery health.

4. Scientific storage and maintenance

when storing batteries for a long time, keep the power between 40% and 60%, and store them in a dry and cool environment to avoid high temperature and humidity.

5. Use high quality materials and processes

by improving the ratio of positive poles, optimizing the electrolyte formula and manufacturing process, manufacturers can improve the stability and durability of battery materials and fundamentally prolong the battery life.

The life of ternary lithium battery is an important index to evaluate its performance and economic value, which is affected by many factors such as material characteristics, service environment, charging and discharging conditions, etc. Understanding the connotation of battery life and its influencing mechanism is helpful for users to use and maintain the battery reasonably and prolong its service cycle. At the same time, adopting scientific charging and discharging strategy, perfect battery management system and good storage conditions are the key to ensure the long-term stable operation of ternary lithium batteries.