1. Working principle of lithium-ion battery

Lithium-ion battery is a kind of rechargeable battery. Compared with most commercial rechargeable batteries, lithium-ion battery is characterized by high energy density, long cycle life and high energy efficiency. The charging cycle of lithium-ion batteries mainly relies on the continuous embedding and detaching of lithium ions from the electrode material to realize.

Initially, lithium-ion batteries were designed to use lithium monomers as the anode material to generate lithium ions by continuously emitting electrons, and these lithium ions and electrons would move into the anode region through the electrolyte and wires, respectively, to realize the discharge process. However, with the widespread use of lithium-ion batteries, it has been found that when lithium monomer is used as the negative electrode, the metal is easily altered by the charging cycle. Therefore, the common lithium batteries on the market today use cobalt oxide and a small amount of lithium monomer as the positive electrode, graphite as the negative electrode, and lithium salt solution as the battery electrolyte. When such batteries are charged, these lithium ions are transported through the electrolyte to the positive electrode. During the charging process, the energy from the external power source will force the electrons inside the battery to flow from the positive electrode to the negative electrode, and to balance the charge in the future, the lithium ions in the electrolyte will migrate from the positive electrode to the negative electrode. And this kind of battery is also called lithium-ion battery because of the abundance of lithium ions in it.

2. Components of lithium-ion battery

2.1 Cathode

The cathode material of lithium-ion batteries is usually a compound with lithium, and the lithium is constantly embedded and detached from the cathode material during the charging and discharging process. The cathode materials commonly used for lithium-ion are divided into three types: stereolamellar oxides, spinel oxides, and oxygen-containing anionic oxides.

2.1.1 Stereolamellar oxides as cathode materials

Lithium-ion battery was invented at the beginning of the three-dimensional layered oxide as cathode material, which is represented by lithium cobaltate and lithium nickelate. These two electrode materials, lithium cobalt has a higher capacity, lower self-discharge rate and other excellent performance. However, the price of cobalt is relatively expensive, further increasing the production cost of the battery. Therefore, the current market common three-dimensional layer oxide lithium-ion batteries will be used to reduce the cobalt content, increase the nickel content of the way to reduce battery costs.

2.1.2 Spinel oxide as cathode material

Common spinel oxide is manganese spinel, the use of manganese spinel as the cathode of the battery compared to cobalt, nickel and other expensive three-dimensional layered oxide can save more costs for battery manufacturers. Another advantage is that this cathode material does not require high voltage to realize the embedding of lithium ions.

2.1.3 Use of oxygenated anions as cathode materials

Oxygen-containing anions such as lithium iron phosphate can also be used as cathode materials for lithium-ion batteries. Compared with their corresponding oxides, these oxygen-containing anions can help the redox reaction potential of lithium ions to shift positively. Secondly, the use of oxygen-containing anions to form cathode materials is more stable and safer than using their corresponding oxides directly. Currently, the popular lithium iron phosphate batteries are used as the main candidate for stationary energy storage in many industries due to their excellent performance such as low price, high stability and long cycle life. However, it is worth noting that the electronic conductivity of these oxygen-containing anionic materials is poor, and the electron transfer efficiency inside the battery is low, so it is necessary to cover a layer of conductive material on the cathode material when it is in use, so as to improve the conductivity.

2.2 Anode

The anode material of lithium-ion battery is generally used to adsorb the lithium ions and electrons moving from the cathode, usually made of other carbon materials such as graphite. However, with the development of lithium-ion batteries, more and more new materials are being tried as anode materials.

2.2.1 Using graphite and other carbon materials as anode materials

Graphite, as the most widely used anode material in lithium-ion batteries, is inexpensive and has a high energy density. However, the battery must enter the outer edge of the graphite sheet to be embedded when charging, and this step will consume a long time, making there will be a large number of lithium ions congested in the edge of the graphite sheet. Therefore, the use of graphite and other carbon materials as lithium-ion battery anode charging time is longer.

2.2.2 Use of other new materials as anode materials

2.3 Electrolyte

2.3.1 Liquid electrolyte

The electrolytes of traditional lithium-ion batteries generally use lithium salt solution as the liquid electrolyte. The presence of these liquid electrolytes allows lithium ions to move between the cathode and anode during the charging and discharging process. The advantage is the high conductivity.

2.3.2 Solid electrolytes

The recent R&D direction of lithium-ion batteries also involves solid electrolyte materials, and the most promising development at present is ceramic electrolyte. Ceramic electrolytes are mostly composed of lithium oxides, because the electrolyte material itself contains lithium, which makes the battery charge and discharge process, lithium ions can better move in this solid electrolyte. In addition, a significant advantage of the solid electrolyte is that it does not leak, which is also a major safety issue that needs to be faced when using liquid electrolytes.

3. Different Shapes of Lithium Ion Batteries

Lithium-ion batteries on the market can be designed in different shapes in order to suit many different usage scenarios. There are three main common shapes: cylindrical, square, and pouch-type soft pack.

3.1 Cylindrical lithium-ion batteries

The most common type of lithium ion battery is the cylindrical lithium ion battery. Which is divided into large cylindrical and small cylindrical, the two are basically no different in the way of composition. Perspective through the positive electrode, ionic septum, negative electrode, ionic septum rolled into a cylindrical, and then the battery as a whole into a cylindrical container. Whereas small cylindrical lithium ion batteries generally do not come with threaded terminals, large cylindrical lithium ion batteries generally come with a large threaded terminal. Cylindrical lithium-ion batteries are the most common shape of lithium-ion batteries in our daily lives, and they can be made into different sizes and capacities for use in different situations. The advantage of these cylindrical batteries lies in the fact that they can be produced quickly and can be mechanized to a high degree. However, it is worth noting that the radial temperature difference of the battery can be significant in the case of high efficiency discharge.

3.2 Square lithium-ion batteries

Square lithium-ion batteries are generally used in applications that require as much capacity as possible in a small space, such as laptop computers. Although square Li-ion batteries are larger than cylindrical Li-ion batteries, they contain more lithium. As a result, each square cell allows for a larger battery pack configuration while providing more power. Therefore, square lithium-ion batteries are typically connected together to form a larger lithium-ion battery pack for energy storage.

3.3 Pouch-type flexible pack lithium-ion batteries

Pouch-type soft-packed lithium-ion batteries mainly consist of an aluminium foil pouch as well as contents. Each section has two terminals, this pouch type soft pack lithium ion battery can do in the form factor allows the maximum content of lithium, and often designed to be directly into the power supply part of the application without allowing a hard metal shell. It is thanks to its characteristics do not need shell; pouch lithium-ion batteries have the highest energy density.

4. Advantages and disadvantages of lithium-ion batteries

4.1 Advantages of lithium-ion batteries

4.1.1 High energy density

Compared to other rechargeable batteries, lithium-ion batteries have the highest energy density of any commercial battery technology. This means that it can store more power in the same volume, which makes it ideal for home energy storage and as a backup energy battery.

4.1.2 Lower maintenance costs

Lithium-ion batteries do not require regular charging and discharging cycles to maintain battery life, and the efficiency of lithium-ion batteries does not diminish as their life span decreases, so the maintenance costs of lithium-ion batteries are reduced to a lower cost level.

4.1.3 No memory effect

First of all, we need to know that the memory effect is a harmful process in rechargeable batteries. As the battery undergoes repeated charging and discharging cycles, this memory effect causes the battery to memorize the lower capacity, which affects the efficiency of the battery, but lithium-ion batteries do not have this memory effect.

4.1.4 Lower self-discharge rate

General lithium-ion batteries monthly self-discharge rate of only one to two percent, even if not used for a long time, but also because of self-generation will not bring damage and inconvenience to the user.

4.2 Disadvantages of lithium-ion batteries

4.2.1 Higher production cost

As the general lithium-ion battery contains nickel, cobalt and other rare earth elements, which makes its production and production costs higher.

4.2.2 Need to install other control systems

In order to prevent lithium-ion batteries in the use of over-charging, over-discharging and heating, general lithium-ion batteries need to be equipped with battery management systems, temperature sensors, charge status monitors, etc. used to monitor the charging and the use of voltage and current and monitor the temperature at any time, to prevent the battery from bringing adverse effects and thus reducing the life of the battery.

5. Lithium-ion battery applications in the industry

5.1 Solar power generation system storage

Solar power systems installed battery packs need to be responsible for temporary storage of electricity during the day, and then discharged at night to supply the family use. Therefore, the battery packs used in solar power generation systems need to meet a high number of cycles, and in order to save costs and maintenance costs in the later stages, the need to choose the type of solar batteries that are not easily damaged and do not require maintenance. Lithium-ion battery is undoubtedly the best choice for solar power system battery pack.

5.2 Caravan power supply

For RVs that need to use electrical appliances in off-grid situations, the higher energy density of lithium-ion batteries, higher security determines the use of lithium-ion batteries for its power supply is a good choice.

6. Future development of lithium-ion batteries

For the future development of lithium-ion batteries, must be towards the direction of improving efficiency and enhancing the use of safety. For example, the research and development of ceramic and other materials such as solid electrolyte or other materials of the gel electrolyte can reduce the lithium-ion battery in the use of electrolyte leakage, gas leakage, etc. may lead to the probability of explosion and fire, and to further reduce the battery needs to be installed within the safety measures, to a certain extent, will reduce the cost of the battery.