Factors Affecting the Cycle Life of Lead Acid replacements and Their Life Prediction
Lead Acid replacements are widely used in various fields such as electronic products, power tools, electric vehicles, and energy storage due to their high energy density, no memory effect, small self-discharge, and long cycle life. The performance of the battery can be divided into two categories: electrical performance and reliability. Life is one of the important indicators to measure its electrical performance.
For energy-type batteries, it is generally considered that the life of the battery is terminated when the usable capacity of the battery decays to 80% of the initial capacity. The life of a battery includes cycle life and calendar life. The former refers to the number of cycles that the battery cycles with a certain charge-discharge regime to the end of its life, while the latter refers to the time required for the battery to be stored in a certain state to the end of its life.
Many complex physical and chemical reactions occur during the charging and discharging process of Lead Acid replacements, so there are many factors that affect the cycle life of Lead Acid replacements. On the other hand, cycle life testing is often time-consuming and costly. Correct assessment of battery life has a certain guiding role in the production and development of Lead Acid replacements and battery health management systems.
1 Aging and decay of battery materials
The materials inside the Lead Acid replacement mainly include: positive and negative active materials, binders, conductive agents, current collectors, separators and electrolytes. During the use of Lead Acid replacements, these materials will be accompanied by a certain degree of decline and aging. Tang Zhiyuan et al. believe that the capacity attenuation factors of lithium manganate batteries include: dissolution of positive electrode material, phase change of electrode material, decomposition of electrolyte, formation of interface film and current collector corrosion.
Vetter et al. conducted a systematic and in-depth analysis of the change mechanism of the positive electrode, negative electrode and electrolyte of the battery during cycling. The authors believe that the formation and subsequent growth of the negative SEI film will be accompanied by irreversible loss of active lithium, and the SEI film does not function as a true solid electrolyte, except for lithium ions, the diffusion and migration of other substances can lead to gas generation and particle rupture. In addition, the change in material volume and the precipitation of metallic lithium during cycling can also lead to capacity loss.