The so-called polymer lithium battery refers to a lithium ion battery that uses a polymer as an electrolyte, and is divided into two types: “semi-polymer” and “all-polymer”. “Semi-polymer” refers to coating a layer of polymer (usually PVDF) on the barrier film to make the cell’s adhesion stronger, the battery can be made harder, and the electrolyte is still a liquid electrolyte. The “all polymer” refers to the use of polymer to form a gel network inside the cell, and then inject electrolyte to form an electrolyte. Although “all-polymer” batteries still use liquid electrolyte, the amount is much smaller, which greatly improves the safety performance of lithium-ion batteries. As far as I know, only SONY is currently mass producing “all-polymer” lithium-ion batteries. From another aspect, polymer battery refers to the use of aluminum-plastic packaging film as the outer packaging of lithium-ion batteries, also commonly known as soft-pack batteries. This kind of packaging film is composed of three layers, namely PP layer, Al layer and nylon layer. Because PP and nylon are polymers, this kind of battery is called polymer battery.

The difference between lithium ion battery and polymer lithium battery

1. The raw materials are different. The raw material of lithium ion batteries is electrolyte (liquid or gel); the raw materials of polymer lithium battery are electrolytes including polymer electrolyte (solid or colloidal) and organic electrolyte.

2. In terms of safety, lithium-ion batteries are simply blasted in a high-temperature and high-pressure environment; polymer lithium batteries use aluminum plastic film as the outer shell, and when organic electrolytes are used inside, they will not burst even if the liquid is hot.

3. Different shapes, polymer batteries can be thinner, arbitrarily shaped, and arbitrarily shaped. The reason is that the electrolyte can be solid or colloidal rather than liquid. Lithium batteries use electrolyte, which requires a solid shell. The secondary packaging contains the electrolyte.

4. The battery cell voltage is different. Because polymer batteries use polymer materials, they can be made into a multi-layer combination to achieve high voltage, while the nominal capacity of lithium battery cells is 3.6V. If you want to achieve high voltage in practice, Voltage, you need to connect multiple cells in series to form an ideal high-voltage work platform.

5. The production process is different. The thinner the polymer battery, the better the production, and the thicker the lithium battery, the better the production. This allows the application of lithium batteries to expand more fields.

6. Capacity. The capacity of polymer batteries has not been effectively improved. Compared with standard capacity lithium batteries, there is still a reduction.

Advantages of polymer lithium battery

1. Good safety performance. The polymer lithium battery uses aluminum-plastic soft packaging in structure, which is different from the metal shell of the liquid battery. Once a safety hazard occurs, the lithium ion battery is simply blasted, while the polymer battery will only blow up, and at most it will be burned.

2. Small thickness can be made thinner, ultra-thin, thickness can be less than 1mm, can be assembled into credit cards. There is a technical bottleneck for the thickness of ordinary liquid lithium batteries below3.6mm, and the 18650 battery has a standardized volume.

3. Light weight and large capacity. The polymer electrolyte battery does not need a metal shell as a protective outer packaging, so when the capacity is the same, it is 40% lighter than a steel shell lithium battery and 20% lighter than an aluminum shell battery. When the volume is generally large, the capacity of the polymer battery is larger, about 30% higher.

4. The shape can be customized. The polymer battery can add or reduce the thickness of the battery cell according to practical needs. For example, a new notebook of a famous brand uses a trapezoidal polymer battery to make full use of the internal space.

Defects of polymer lithium battery

(1) The main reason is that the cost is higher, because it can be planned according to the customer’s needs, and the R&D cost here must be included. In addition, the variety of shapes and varieties have led to the correct and wrong specifications of various tooling and fixtures in the production process, and correspondingly increased costs.

(2) The polymer battery itself has poor versatility, which is also brought about by sensitive planning. It is often necessary to plan one for customers from scratch for the difference of 1mm.

(3) If it is broken, it will be completely discarded, and protection circuit control is required. Overcharge or overdischarge will damage the reversibility of the internal chemical substances of the battery, which will seriously affect the battery life.

(4) The lifespan is shorter than 18650 because of the use of different plans and materials, some have liquid inside, some are dry or colloidal, and the performance is not as good as 18650 cylindrical batteries when discharged at high current.