What is the difference between polymer lithium battery and lead-acid battery?
Although they are both batteries, their biggest difference lies in the difference in manufacturing materials and discharge performance, which makes their application fields different.
lithium battery
1. The difference in materials between lithium batteries and lead-acid batteries
(1) Lithium battery manufacturing materials
Lithium batteries include polymer lithium batteries, lithium cobalt oxide batteries, ternary lithium batteries and lithium iron phosphate batteries. The main materials used in their respective manufacturing: positive electrode material, negative electrode material, separator and electrolyte.
1) Among the cathode materials, the most commonly used materials are lithium cobaltate, lithium manganate, lithium iron phosphate and ternary materials (a polymer of nickel cobalt manganese). Cathode materials occupies a large proportion (the mass ratio of positive and negative materials is 3:1~4:1), because the performance of cathode materials directly affects the performance of lithium-ion batteries, and its cost directly determines the cost of the battery.
2) Among the anode materials, the current anode materials are mainly natural graphite and artificial graphite. The anode materials being explored include nitrides, PAS, tin-based oxides, tin alloys, nano-anode materials, and other intermetallic compounds. As one of the four major constituent materials of lithium batteries, anode materials play an important role in improving battery capacity and cycle performance, and are at the core of the middle reaches of the lithium battery industry.
3) The market-oriented diaphragm materials are mainly Polyolefin diaphragms mainly composed of polyethylene (PE) and polypropylene (PP). In the structure of lithium batteries, the diaphragm is one of the key inner components. The performance of the diaphragm determines the interface structure and internal resistance of the battery, and directly affects the battery's capacity, cycle and safety performance. A diaphragm with excellent performance plays an important role in improving the overall performance of the battery.
4) Electrolyte is generally prepared from high-purity organic solvents, electrolyte lithium salt, necessary additives and other raw materials under certain conditions and in certain proportions. The electrolyte plays a role in conducting ions between the positive and negative electrodes of the lithium battery, which guarantees that the lithium ion battery obtains the advantages of high voltage and high specific energy.
Lead-acid batteries
(2) Lead-acid battery manufacturing materials
The composition of lead-acid batteries: plate, separator, shell, electrolyte, lead connecting strip, pole, etc.
1) Positive and negative plates
Classification and composition: The polar plates are divided into positive and negative plates, both of which are composed of a grid frame and an active material filled on it.
Function: In the process of battery charging and discharging, the mutual conversion of electric energy and chemical energy is realized by the chemical reaction between the active material on the electrode plate and the sulfuric acid in the electrolyte.
Color distinction: The active material on the positive plate is lead dioxide (PbO2), which is dark brown; the active material on the negative plate is spongy pure lead (Pb), which is blue-gray.
The role of the grid: to contain the active material and to shape the plate.
Plate group: In order to increase the capacity of the battery, multiple positive and negative plates are welded in parallel to form a positive and negative plate group.
Special requirements for installation: during installation, the positive and negative plates are inserted into each other, and the separator is inserted in the middle. In each single cell, the number of negative plates is always one more than the number of positive plates.
2) Partition
Function: In order to reduce the internal resistance and size of the battery, the positive and negative plates inside the battery should be as close as possible; in order to avoid contact with each other and short circuit, the positive and negative plates should be separated by separators.
Material requirements: The separator material should have porosity and permeability, and the chemical properties should be stable, that is, it has good acid resistance and oxidation resistance.
Materials: Commonly used partition materials include wooden partitions, microporous rubber, microporous plastics, fiberglass and cardboard.
Installation requirements: The grooved side of the separator should face the positive plate during installation.
3) Shell
Function: used to hold the electrolytic solution and the plate assembly
Material: Made of materials with acid resistance, heat resistance, shock resistance, good insulation and certain mechanical properties.
Structural features: The shell is an integral structure, the inside of the shell is divided into 3 or 6 single cells that are not connected to each other by partition walls, and there are protruding ribs at the bottom to hold the plate assembly. The space between the ribs is used to accumulate the fallen active material to prevent short circuit between the pole plates. After the pole plates are installed in the shell, the upper part is sealed with a battery cover made of the same material as the shell. There is a filling hole corresponding to the top of each cell on the battery cover, which is used to add electrolyte and distilled water, and can also be used to check the height of the electrolyte level and measure the relative density of the electrolyte.
4) Electrolyte
Role: The electrolyte plays a role in the conduction between ions and participates in the chemical reaction in the conversion process of electrical energy and chemical energy, that is, the electrochemical reaction of charging and discharging.
Ingredients: It is made up of pure sulfuric acid and distilled water in a certain proportion, and its density is generally 1.24～1.30g/ml.
Special attention: the purity of the electrolyte is an important factor affecting the performance and service life of the battery.
2. The difference in discharge performance between lithium batteries and lead-acid batteries
1) In the low temperature environment of the battery, the discharge performance of lithium batteries is much better than that of lead-acid batteries in terms of low temperature resistance;
2) In terms of cycle life, lithium batteries are about twice as long as lead-acid batteries;
3) In terms of working voltage, lithium battery is 3.7V, lead-acid battery is 2.0V, and the discharge platform is higher than that of lead-acid battery;
4) In terms of battery energy density, lithium batteries are much higher than lead-acid batteries;
5) Under the same capacity and voltage, lithium batteries are lighter in weight and more flexible than lead-acid batteries in size and shape;
Despite this, lead-acid batteries still rely on a series of advantages such as strong high-current discharge performance, stable voltage characteristics, wide temperature application range, large single battery capacity, high safety, abundant raw materials, renewable utilization, and low price. Most traditional fields and some emerging application fields occupy a firm position.
3) The difference between lithium batteries and lead-acid batteries in application areas
As lithium batteries have more flexible customization in energy density, size, and shape, they tend to be portable and smart devices in the application field, such as smart wearable 3C products, portable power banks, etc.
Lead-acid batteries are single-shaped, large and bulky. Most of them are used in energy storage devices, and those that are not portable but cannot always use AC power.
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