Structure, characteristics, performance and safety of polymer battery

Structure, characteristics, performance and safety of polymer battery

Structure of polymer battery

 

The figure shows the structure of a laminated lithium polymer battery. This is a structure of a battery consisting of LiCoO2, gel-type polymer electrolyte, carbon, and graphite battery components that bend or overlay them into a flat panel and are encapsulated with an aluminum deposition.
People are studying polymer batteries using Ni or Mn materials as positive electrode active substances, but they still cannot reach the practical level. The anode active material is a graphite material with flat discharge voltage curves and a hard carbon material with steady discharge slope. Currently, there are only two types of lithium polymer battery available: 1.5mm in thickness, 3.6 MAH in capacity, mah in thickness for carrying phones, and MAH in capacity.

In 1973, PV. Right discovered the conduction of ions in polymer materials. In 1978, M. B. Armand and others proposed the application of Solid Electrolyte in battery and electronic devices. Since then, the development and research of polymer battery has become increasingly active.
Polymer electrolytes are divided into three types: Dry polymers, gel polymers with organic solvents added to dry polymers, and multi-pass polymer electrolytes with organic solvents added to porous matrix materials represented by PVDF. Table 1 shows the performance of these three polymer electrolytes. The ion conductivity of the Initial dry polymer is 10-7 S/cm. After improvement, the conductivity at room temperature reaches 10-4 S/cm. However, it is difficult to apply to electronic devices working at normal temperature. The addition of soluble gel-type polymer electrolyte in dry polymers has increased the conductivity to 10-3 S/cm, making it a huge step towards practical use.
The polymer electrolyte used by some manufacturers is a gel polymer electrolyte that contains the soluble polyethylene oxide and polypropylene oxide which are randomly overlapped.

Performance of lithium polymer battery
Figure 4 shows the charging characteristics of 0.2cma and 0.5cma charged with constant current and constant voltage. To maintain the basic performance of the battery, set the maximum charging voltage to 4.1 v. Figure 5 shows the discharge characteristics from 0.2cma to 1cma. Figure 6 shows the discharge characteristics from 60 ℃ to 10 ℃. Compare the discharge characteristics at 25 ℃, the discharge capacity at-10 ℃ reaches 85%. To maintain the basic performance of the battery, the minimum discharge voltage is set to 27 v. Figure 7 shows the cyclic test performance of the battery. Placement of 28-day battery photos at 20 ℃ and 60 ℃ 1 Performance evaluation results of lithium polymer battery produced by Yuasa Japan are shown in figure 8. At 20 ℃, the battery retention rate is about 95%, which is similar to that of lithium-ion battery.

 

Figure 4 charging characteristics of lithium polymer battery

 

Figure 5 discharge characteristics of lithium polymer battery

 

Figure 6 discharge temperature characteristics of lithium polymer battery

 

Figure 7pf500174 (36 V, 200 MAH) lithium polymer
Battery life (Cyclic charge/discharge)

Figure 8 lithium polymer battery capacity retention

Figure 9nps-24v80 Discharge Characteristics

 

Figure 10 energy density of various lithium batteries

Safety of lithium polymer battery
Safety is an important performance of all secondary batteries. A battery that cannot be safely used will not be popular no matter how good its performance is. Table 2 shows the safety comparison between lithium-ion battery (square-type) and lithium-polymer battery with no protection circuit. It can be seen that compared with liquid battery, lithium polymer battery is safer.
 
Table 2 Comparison of the safety of Lithium-polymer battery and square lithium-ion battery
(Bare batteries with no protection circuit are used)

Rating items	Lithium polymer battery		Lithium-ion battery
Dingtalk Test	No cracking, no fire, no liquid leakage (no temperature rise 20℃ )	○	Cracked white smoke leakage (temperature rises 250 ℃ )	×
Hot Plate heating ( 200 ℃ )	No cracking, no fire, no liquid leakage	○	Cracking and fire Leakage	×
External Short Circuit	No cracking, no fire, no liquid leakage (no temperature rise 20℃ )	○	No cracking, no fire, liquid leakage (temperature rise 100 ℃ Left and right)	△
Overcharging	No cracking, no fire, no liquid leakage (no temperature rise 20℃ )	○	Liquid leakage (temperature rise 100 ℃ Left and right)	×

Table 3 shows various safety test results for lithium polymer batteries. The battery size is 74mm × 54mm × 2.2mm, and the capacity is 400 Mah. In a battery with no protection circuit, no cracking or fire is found even if the battery is forced to discharge and charge for 1 CMA for 6 hours. The battery after full charging is placed at 60 ℃ for 2 days, with a 3mm diameter nail piercing, when the temperature reaches about 10 ℃, there is no rupture and fire. In the impact test, although the battery is divided into two sections, there is still no cracking and fire. It can be seen that the lithium polymer battery is more secure than the liquid electrolyte battery. To maintain the basic performance of the battery, this battery is set to prevent overcharging voltage and overdischarge voltage. Photo 1 shows the appearance of a lithium polymer battery produced by Yuasa, Japan. Table 4 shows the performance specifications of the battery.