Characteristics and differences of lithium battery soft pack and hard pack lithium battery

Introduction to Lithium Battery

"Lithium battery" is a type of battery that uses lithium metal or lithium alloy as a negative electrode material and uses a non-aqueous electrolyte solution. In 1912, the lithium metal battery was first proposed and studied by GilbertN. Lewis. In the 1970s, M.S. WhitTIngham proposed and began to study lithium-ion batteries. Due to the very lively chemical properties of lithium metals, the processing, preservation, and use of lithium metals require very high environmental requirements. Therefore, lithium batteries have not been used for a long time. With the development of science and technology, lithium batteries have now become the mainstream.

Lithium batteries can be roughly divided into two categories: lithium metal batteries and lithium ion batteries. Lithium-ion batteries do not contain metallic lithium and can be charged. The fifth-generation lithium metal battery of rechargeable batteries was born in 1996, and its safety, specific capacity, self-discharge rate, and performance price are better than those of lithium-ion batteries. Due to its own high-tech requirements, companies in only a few countries are now producing this lithium metal battery.

Lithium-ion battery structure

Lithium-ion batteries are alternatives to lithium metal batteries that have appeared in previous years. The main components of batteries are positive and negative poles, electrolytes, membranes, and shells.

Positive poles-Carbon poles that can absorb lithium ions are used. When discharged, lithium becomes lithium ions, leaving the battery anode and reaching the cathode of the lithium ion battery.

The negative electrode-The material selects an embedded lithium compound with potential as close as possible to the lithium potential, such as a variety of carbon materials including natural graphite, synthetic graphite, carbon fiber, intermediate phase pellet carbon, etc., and metal oxides.

Electrolytes-A mixed solvent system using alkyl carbonates such as LiPF6 vinyl carbonate, propylene carbonate, and low viscosity diethyl carbonate.

Membrane-The use of polyene microporous membranes such as PE, PP or their composite membranes, especially the PP / PE / PP three-layer diaphragm not only has a low melting point but also has high anti-puncture strength, playing a thermal insurance role.

Shell-steel or aluminum material used, cover assembly with explosion-proof power off function.

Working Principles of Lithium-ion Battery

The working principle of lithium-ion batteries refers to its charging and discharging principle.

When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the resulting lithium ions move through the electrolyte to the negative electrode. The carbon as a negative electrode has a layered structure. It has many micropores. Lithium ions that reach the negative pole are embedded in the micropores of the carbon layer. The more lithium ions embedded, the higher the charging capacity. The chemical reaction that occurs at this time is:

2. Similarly, when the battery is discharged (that is when we use the battery), the lithium ions embedded in the negative carbon layer are removed and moved back to the positive pole. The more lithium ions that return to the positive pole, the higher the discharge capacity. What we usually refer to as battery capacity refers to discharge capacity. The chemical reaction that occurs at this time is:

3. It is not difficult to see that in the process of charging and discharging of lithium ion batteries, lithium ions are in a state of motion from positive to negative to positive. If we compare the lithium-ion battery image to a rocking chair, the two ends of the rocking chair are the two poles of the battery, and the lithium ion is like a good athlete, running back and forth between the two ends of the rocking chair. So experts gave lithium-ion batteries a cute name for a rocking chair battery.

Introduction to Lithium Battery

Lithium batteries are just liquid lithium-ion batteries coated with a polymer shell. In the structure of aluminum plastic film packaging, in the event of safety hazards, the flexible battery will only crack the gas.

Lithium battery parameters

Nominal voltage: 3.7 V

Operating voltage: 2.4 ~ 4.2 V

Nominal capacity: 1250mAh

Standard electrical discharge continuous current: 0.2 C

Maximum continuous discharge current: 0.5 C

Operating temperature: Charging: 0 ~ 45 °C

Discharge: -20 ~ 60 °C

Product Size: MAX9 .5 * 35 * 52 mm

The internal resistance of finished product: ≤ 150mΩ

Over discharge protection voltage 2.5 ± 0.05 V

Lead type: national standard UL1007/24 #, line length 55mm protection parameter: overcharged protection voltage / 4.325 ± 0.025 V per string

Overflow value: 2 ~ 4A

Advantages of Soft Battery

1. Good Safety Performance

Soft pack batteries do not explode like steel shell aluminum shell cores.

2. Lightweight

The weight of the flexible battery is 40 % lighter than that of the same capacity lithium steel shell and 20 % lighter than the aluminum shell battery.

3. Large capacity

Soft pack batteries have a capacity of 10 to 15 % higher than steel shell batteries of the same size and 5 to 10 % higher than aluminum shell batteries.

4. Small internal resistance

The internal resistance of the soft-pack battery is smaller than that of the lithium battery. At present, the internal resistance of the domestic soft-pack battery core can be below 35mΩ, which greatly reduces the battery's self-consumption.

5. Flexible design

The shape of the soft pack battery can be customized according to the customer's needs and a new type of core can be developed.

Deficiencies of soft-pack batteries

The existing soft pack battery core models are few and can not meet the market demand;

Developing new models is expensive.

The difference between a soft and hard pack of lithium battery

The difference between a lithium battery soft pack and a hard pack mainly refers to the material of a lithium battery shell. If it is packaged on the outside, it is not easy to see it. It must be seen that the battery body, the weight of the steel shell battery will be more important than the same volume of battery. However, aluminum shells and soft packaging are not easy to distinguish, but soft packaging batteries will be a little softer than aluminum shell batteries, and it is easy to deform by hand.

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