Lithium battery is a type of battery that uses lithium metal or lithium alloy as the negative electrode material and uses a non-aqueous electrolyte solution. The earliest presented lithium battery came from the great inventor Edison.
Lithium Batteries – Lithium Batteries
lithium battery
Lithium battery is a type of battery that uses lithium metal or lithium alloy as the negative electrode material and uses a non-aqueous electrolyte solution. The earliest presented lithium battery came from the great inventor Edison.
Because the chemical properties of lithium metal are very active, the processing, storage and application of lithium metal have very high environmental requirements. Therefore, lithium batteries have not been used for a long time.
With the development of microelectronics technology in the twentieth century, miniaturized devices are increasing day by day, which puts forward high requirements for power supply. Lithium batteries have then entered a large-scale practical stage.
It was first used in cardiac pacemakers. Because the self-discharge rate of lithium batteries is extremely low, the discharge voltage is steep. It makes it possible to implant the pacemaker into the human body for a long time.
Lithium batteries generally have a nominal voltage higher than 3.0 volts and are more suitable for integrated circuit power supplies. Manganese dioxide batteries are widely used in computers, calculators, cameras, and watches.
In order to develop varieties with better performance, various materials have been studied. And then make products like never before. For example, lithium sulfur dioxide batteries and lithium thionyl chloride batteries are very distinctive. Their positive active material is also a solvent for the electrolyte. This structure is only present in non-aqueous electrochemical systems. Therefore, the study of lithium batteries has also promoted the development of the electrochemical theory of non-aqueous systems. In addition to the use of various non-aqueous solvents, research on polymer thin-film batteries has also been carried out.
In 1992, Sony successfully developed lithium-ion batteries. Its practical application greatly reduces the weight and volume of portable electronic devices such as mobile phones and notebook computers. The use time is greatly extended. Because lithium-ion batteries do not contain heavy metal chromium, compared with nickel-chromium batteries, the pollution to the environment is greatly reduced.
1. Lithium-ion battery
Lithium-ion batteries are now divided into two categories: liquid lithium-ion batteries (LIBs) and polymer lithium-ion batteries (PLBs). Among them, the liquid lithium ion battery refers to the secondary battery in which the Li + intercalation compound is the positive and negative electrodes. The positive electrode selects lithium compound LiCoO2 or LiMn2O4, and the negative electrode selects lithium-carbon interlayer compound. Lithium-ion batteries are an ideal driving force for development in the 21st century because of their high operating voltage, small size, light weight, high energy, no memory effect, no pollution, low self-discharge, and long cycle life.
2. A brief history of lithium-ion battery development
Lithium batteries and lithium ion batteries are new high-energy batteries successfully developed in the 20th century. The negative electrode of this battery is metal lithium, and the positive electrode is MnO2, SOCL2, (CFx)n, etc. It was put into practical use in the 1970s. Because of its high energy, high battery voltage, wide operating temperature range, and long storage life, it has been widely used in military and civilian small electrical appliances, such as mobile phones, portable computers, video cameras, cameras, etc., partially replacing traditional batteries. .
3. Development prospects of lithium-ion batteries
Lithium-ion batteries have been widely used in portable appliances such as laptop computers, video cameras, and mobile communications due to their unique functional advantages. The large-capacity lithium-ion battery developed now has been trialed in electric vehicles, and it is estimated that it will become one of the primary power sources for electric vehicles in the 21st century, and will be used in satellites, aerospace and energy storage.
4. The basic function of the battery
(1) The open circuit voltage of the battery
(2) Internal resistance of the battery
(3) The operating voltage of the battery
(4) Charging voltage
The charging voltage refers to the voltage applied to both ends of the battery by the external power supply when the secondary battery is being charged. The basic methods of charging include constant current charging and constant voltage charging. Generally, constant current charging is used, and its characteristic is that the charging current is stable during the charging process. As the charging progresses, the active material is recovered, the electrode reaction area is continuously reduced, and the polarization of the motor is gradually increased.
(5) Battery capacity
Battery capacity refers to the amount of electricity obtained from the battery, which is usually expressed by C, and the unit is usually expressed by Ah or mAh. Capacity is an important goal of battery electrical performance. The capacity of the battery is usually divided into theoretical capacity, practical capacity and rated capacity.
The battery capacity is determined by the capacity of the electrodes. If the capacities of the electrodes are not equal, the capacity of the battery depends on the electrode with the smaller capacity, but it is by no means the sum of the capacities of the positive and negative electrodes.
(6) Storage function and life of the battery
One of the primary features of chemical power sources is that they can release electrical energy when in use and store electrical energy when not in use. The so-called storage function is the ability to maintain charging for the secondary battery.
Regarding the secondary battery, the service life is an important parameter to measure the battery performance. A secondary battery is charged and discharged once, called a cycle (or cycle). Under a certain charging and discharging criterion, the number of charging and discharging times that the battery can withstand before the battery capacity reaches a certain value is called the operating cycle of the secondary battery. Lithium-ion batteries have excellent storage performance and long cycle life.
Lithium Batteries – Features
A. High energy density
The weight of the lithium-ion battery is half that of the nickel-cadmium or nickel-hydrogen battery of the same capacity, and the volume is 40-50% of the nickel-cadmium and 20-30% of the nickel-hydrogen battery.
B. High Voltage
The operating voltage of a single lithium-ion battery is 3.7V (average value), which is equivalent to three nickel-cadmium or nickel-metal hydride batteries connected in series.
C. No pollution
Lithium-ion batteries do not contain harmful metals such as cadmium, lead, and mercury.
D. Does not contain metallic lithium
Lithium-ion batteries do not contain metallic lithium and are therefore not subject to regulations such as the prohibition of carrying lithium batteries on passenger aircraft.
E. High cycle life
Under normal conditions, lithium-ion batteries can have more than 500 charge-discharge cycles.
F. No memory effect
The memory effect refers to the phenomenon that the capacity of the nickel-cadmium battery is reduced during the charging and discharging cycle. Lithium-ion batteries do not have this effect.
G. Fast charging
Using a constant current and constant voltage charger with a rated voltage of 4.2V can fully charge the lithium-ion battery in one to two hours.
Lithium Battery – Principle and Structure of Lithium Battery
1. Structure and working principle of lithium ion battery: The so-called lithium ion battery refers to a secondary battery composed of two compounds that can reversibly intercalate and deintercalate lithium ions as positive and negative electrodes. People call this lithium-ion battery with a unique mechanism, which relies on the transfer of lithium ions between the positive and negative electrodes to complete the battery charge and discharge operation, as a “rocking chair battery”, commonly known as “lithium battery”. Take LiCoO2 as an example: (1) When the battery is charged, lithium ions are deintercalated from the positive electrode and intercalated in the negative electrode, and vice versa when discharging. This requires an electrode to be in a state of lithium intercalation before assembly. Generally, a lithium intercalation transition metal oxide with a potential greater than 3V relative to lithium and stable in air is selected as the positive electrode, such as LiCoO2, LiNiO2, LiMn2O4, LiFePO4. (2) For materials that are negative electrodes, select intercalable lithium compounds whose potential is as close to the lithium potential as possible. For example, various carbon materials include natural graphite, synthetic graphite, carbon fiber, mesophase spherical carbon, etc. and metal oxides, including SnO, SnO2, Tin composite oxide SnBxPyOz (x=0.4～0.6, y=0.6～0.4, z=(2+3x+5y)/2) etc.
lithium battery
2. The battery generally includes: positive, negative, electrolyte, separator, positive lead, negative plate, central terminal, insulating material (insulator), safety valve ( safetyvent), sealing ring (gasket), PTC (positive temperature control terminal), battery case. Generally, people are more concerned about the positive electrode, the negative electrode, and the electrolyte.
lithium battery
Lithium-ion battery structure comparison
According to different cathode materials, it is divided into iron lithium, cobalt lithium, manganese lithium, etc.;
From the shape classification, it is generally divided into cylindrical and square, and polymer lithium ions can also be made into any shape;
According to the different electrolyte materials used in lithium-ion batteries, lithium-ion batteries can be divided into two categories: liquid lithium-ion batteries (LIB) and solid-state lithium-ion batteries. PLIB) is a kind of solid-state lithium-ion battery.
electrolyte
Shell/Package Barrier Current Collector
Liquid lithium-ion battery Liquid stainless steel, aluminum 25μPE copper foil and aluminum foil polymer lithium-ion battery colloidal polymer aluminum/PP composite film without barrier or single μPE copper foil and aluminum foil
Lithium Batteries – The Function of Lithium Ion Batteries
1. High energy density
Compared with NI/CD or NI/MH batteries of the same capacity, lithium-ion batteries are lighter in weight, and their volume specific energy is 1.5 to 2 times that of these two types of batteries.
2. High voltage
Lithium-ion batteries use highly electronegative element-containing lithium electrodes to achieve terminal voltages as high as 3.7V, which is three times the voltage of NI/CD or NI/MH batteries.
3. Non-polluting, environmentally friendly
4. Long cycle life
The life span exceeds 500 times
5. High load capacity
Lithium-ion batteries can be continuously discharged with a large current, so that this battery can be used in high-power appliances such as cameras and laptop computers.
6. Excellent security
Because of the use of excellent anode materials, the problem of lithium dendrite growth during battery charging is overcome, which greatly improves the safety of lithium-ion batteries. At the same time, special recoverable accessories are selected to ensure the safety of the battery during use.
Lithium battery – Lithium ion battery charging method
Method 1. Before the lithium-ion battery leaves the factory, the manufacturer has carried out activation treatment and pre-charged, so the lithium-ion battery has residual power, and the lithium-ion battery is charged according to the adjustment period. This adjustment period needs to be carried out 3 to 5 times completely. Discharge.
Method 2. Before charging, the lithium-ion battery does not need to be specially discharged. Improper discharge will damage the battery. When charging, try to use slow charging and reduce fast charging; the time should not exceed 24 hours. Only after the battery has undergone three to five complete charge and discharge cycles will its internal chemicals be fully “activated” for optimal use.
Method 3. Please use the original charger or a reputable brand charger. For lithium batteries, use a special charger for lithium batteries and follow the instructions. Otherwise, the battery will be damaged or even risked.
Method 4. The newly purchased battery is lithium ion, so the first 3 to 5 times of charging is generally called the adjustment period, and it should be charged for more than 14 hours to ensure that the activity of lithium ions is fully activated. Lithium-ion batteries have no memory effect, but have strong inertness. They should be fully activated to ensure the best performance in future applications.
Method 5. The lithium-ion battery must use a special charger, otherwise it may not reach the saturation state and affect its function. After charging, avoid placing it on the charger for more than 12 hours, and separate the battery from the mobile electronic product when it is not used for a long time.
Lithium battery – use
With the development of microelectronics technology in the twentieth century, miniaturized devices are increasing day by day, which puts forward high requirements for power supply. Lithium batteries have then entered a large-scale practical stage.
It was first used in cardiac pacemakers. Because the self-discharge rate of lithium batteries is extremely low, the discharge voltage is steep. It makes it possible to implant the pacemaker into the human body for a long time.
Lithium batteries generally have a nominal voltage higher than 3.0 volts and are more suitable for integrated circuit power supplies. Manganese dioxide batteries are widely used in computers, calculators, cameras, and watches.
Application example
1. There are many battery packs as replacements for battery pack repairs: such as those used in notebook computers. After repairing, it is found that when this battery pack is damaged, only individual batteries have problems. It can be replaced with a suitable single-cell lithium battery.
2. Making a high-brightness miniature torch The author once used a single 3.6V1.6AH lithium battery with a white super-brightness light-emitting tube to make a miniature torch, which is easy to use, compact and beautiful. And because of the large battery capacity, it can be used for half an hour every night on average, and it has been used for more than two months without charging.
3. Alternative 3V power supply
Because the single-cell lithium battery voltage is 3.6V. Therefore, only one lithium battery can replace two ordinary batteries to supply power to small household appliances such as radios, walkmans, cameras, etc., which is not only light in weight, but also lasts for a long time.
Lithium-ion battery anode material – lithium titanate
It can be combined with lithium manganate, ternary materials or lithium iron phosphate and other positive materials to form 2.4V or 1.9V lithium ion secondary batteries. In addition, it can also be used as a positive electrode to form a 1.5V lithium battery with metal lithium or lithium alloy negative electrode secondary battery.
Because of the high safety, high stability, longevity and green characteristics of lithium titanate. It can be predicted that lithium titanate material will become the negative electrode material of a new generation of lithium ion batteries in 2-3 years and be widely used in new power vehicles, electric motorcycles and those requiring high safety, high stability and long cycle. field of application. The operating voltage of lithium titanate battery is 2.4V, the highest voltage is 3.0V, and the charging current is up to 2C.
Lithium titanate battery composition
Positive electrode: lithium iron phosphate, lithium manganate or ternary material, lithium nickel manganate.
Negative electrode: lithium titanate material.
Barrier: The current lithium battery barrier with carbon as the negative electrode.
Electrolyte: Lithium battery electrolyte with carbon as the negative electrode.
Battery case: Lithium battery case with carbon as the negative electrode.
The advantages of lithium titanate batteries: choosing electric vehicles to replace fuel vehicles is the best choice to solve urban environmental pollution. Among them, lithium-ion power batteries have attracted extensive attention of researchers. In order to meet the requirements of electric vehicles for on-board lithium-ion power batteries, research and development Negative materials with high safety, good rate performance and longevity are its hot spots and difficulties.
Commercial lithium-ion battery negative electrodes mainly use carbon materials, but there are still some disadvantages in the application of lithium batteries using carbon as the negative electrode:
1. Lithium dendrites are easily precipitated during overcharging, resulting in a short circuit of the battery and affecting the safety function of the lithium battery;
2. It is easy to form SEI film, resulting in low initial charge and discharge power and large irreversible capacity;
3. That is, the platform voltage of carbon materials is low (close to metal lithium), and it is easy to cause the decomposition of the electrolyte, which will bring security risks.
4. In the process of lithium ion insertion and extraction, the volume changes greatly, and the cycle stability is poor.
Compared with carbon materials, spinel-type Li4Ti5012 has significant advantages:
1. It is zero-strain material and has good circulation performance;
2. The discharge voltage is stable, and the electrolyte will not decompose, improving the safety performance of lithium batteries;
3. Compared with carbon anode materials, lithium titanate has a high lithium ion diffusion coefficient (2*10-8cm2/s), and can be charged and discharged at a high rate.
4. The potential of lithium titanate is higher than that of pure metal lithium, and it is not easy to generate lithium dendrites, which provides a basis for ensuring the safety of lithium batteries.
maintenance circuit
It consists of two field effect transistors and a dedicated maintenance integrated block S-8232. The overcharge control tube FET2 and the overdischarge control tube FET1 are connected in series to the circuit, and the battery voltage is monitored and controlled by the maintenance IC. When the battery voltage rises to 4.2V , the overcharge maintenance tube FET1 is turned off, and the charging is terminated. In order to avoid malfunction, a delay capacitor is generally added to the external circuit. When the battery is in a discharged state, the battery voltage drops to 2.55.