What is the power bank?
It is a portable power charger that can store their own electrical energy and be carried around, mainly is used for charging mobile phone, tablet and other consumer electronics products. Its main components include: Case, battery cells used for energy storage, circuit board with power control, input and output, converters and so on.
About lithium-ion battery
Lithium-ion batteries: The electrolyte of lithium-ion batteries is liquid, usually using a liquid electrolyte. The positive electrode material can be lithium cobalt oxide, lithium manganese oxide, ternary material, or lithium iron phosphate. The negative electrode material is graphite. Easy to explode in high temperature and pressure environments.
About polymer lithium battery
Polymer lithium battery is a type of lithium-ion battery that uses polymer electrolytes. The raw materials include polymer electrolytes (solid or colloidal) and organic electrolytes.
Polymer lithium batteries use aluminum-plastic film as the outer shell, and when organic electrolytes are used internally, even if the liquid is very hot, it will not explode, but it will swell.
Polymer lithium batteries cycle time is usually around 500 times, but the actual achievable frequency is influenced by various factors, including usage environment, charging method, and battery quality.
Polymer lithium batteries have various obvious advantages, such as high energy density, miniaturization, ultra-thinness, lightweight, high safety, and low cost. Due to its excellent performance, which are widely used in mobile devices including mobile phone, tablet, power bank, smartwatches, and other electronic products.
Due to the safety issue of power bank, nowadays, polymer lithium batteries are the first option to be chosen as components of power bank.
Lithium battery chemical properties
All rechargeable batteries are consumables, and as the battery chemical age increasing, its performance will decrease. As the chemical age of lithium batteries increases, the amount of electricity they can store will decrease, leading to a shortened time for devices to be used before they need to be recharged.
One factor that affects battery power output is impedance, which may increase when the chemical age of the battery is too high. In low battery conditions and low-temperature environments, the impedance of the battery will temporarily increase, and coupled with a higher chemical age, the increase in impedance will be more pronounced. These are the chemical characteristics of batteries, which are applicable to all lithium-ion batteries in the industry.
Self-discharging of polymer lithium batteries
The self-discharge phenomenon of a battery refers to the spontaneous loss of its capacity when the battery is placed in an open circuit, also known as the charge holding capacity. Self-discharge reaction is inevitable, which not only leads to a decrease in the capacity of the battery itself, but also seriously affects the grouping and cycle life of the battery. Long term self-discharge can cause over discharge and result in battery failure. The self-discharge rate of polymer lithium batteries is generally 2% to 5% per month.
Self-discharge can generally be divided into two types: reversible Self-discharge and irreversible Self-discharge. The reversible Self-discharge can compensate for the loss of capacity reversibly, and its principle is similar to the normal discharge reaction of a battery. The Self-discharge that cannot be compensated for due to loss of capacity is called irreversible Self-discharge, which is mainly caused by irreversible reactions occurring inside the battery, including reactions between the positive electrode and electrolyte, reactions between the negative electrode and electrolyte, reactions caused by impurities in the electrolyte, and irreversible reactions caused by micro short circuits caused by impurities carried during production.