Analysis of parameters, advantages and disadvantages of lithium manganese oxide batteries
Lithium manganese oxide battery parameters:
Nominal voltage: 3.7v
Output voltage range: 2.5~4.2v Nominal capacity: 7500mAh
Standard continuous discharge current: 0.2C
Maximum continuous discharge current: 1C
Working temperature: Charging: 0~45℃
Discharge: -20~60℃
Product size: MAX 19.2*56.5*69.5mm
Finished product internal resistance: ≤200mΩ
Lead wire model: National standard wire UL3302/26#, wire length 50mm, white wire is 10K NTC
Protection board parameters: (Each parameter can be set according to customer products)
Overcharge protection voltage/each string 4.28±0.025V
Over discharge protection voltage 2.4±0.1V
Overcurrent value: 2~4A
Analysis of the advantages and disadvantages of lithium mang
There are three types of lithium manganese oxide: 1. Layered lithium manganese oxide LiMnO2, with a theoretical capacity of 285mA·h/g and a voltage platform of 4V. The layered structure is difficult to synthesize and is unstable. It is very easy to generate Li2Mn2O4 spinel structure, which leads to a decrease in voltage platform, poor stability, and irreversible capacity decay.
2 High-voltage spinel lithium manganese oxide LiMn2O4, theoretical capacity 148mA·h/g, voltage platform 4.15. Poor high-temperature performance, severe capacity decay above 55°C. It is also easy to generate Li2Mn2O4 spinel structure, resulting in a decrease in voltage platform, poor stability, and irreversible capacity decay. This is the type of lithium manganese oxide currently used in industry.
3 Spinel lithium manganese oxide Li2Mn2O4 has low voltage (3V), low capacity and poor cycle. We are studying how to avoid its production.
Ternary: In order to solve the defects of layered lithium manganese oxide, the ternary material LiNiCoMnO2 (LiNiCoAlO2) was invented by doping metal elements. It takes into account the high capacity and high voltage of lithium nickel oxide, the high voltage and high safety of lithium manganese oxide, and the good cyclicity of lithium cobalt oxide. At the same time, it overcomes the shortcomings of lithium manganese oxide, lithium nickel oxide, which are difficult and unstable to synthesize, and lithium cobalt oxide, and has become the current mainstream positive electrode material. The theoretical capacity is 280mA·h/g, the voltage is 2.7~4.2, and the actual capacity is about 160mA·h/g.
In the next few years, the current ternary battery will basically be eliminated in three years, with high nickel and NCA taking the lead. In 10 years, it is estimated that the entire ternary battery will be eliminated, and a new battery system will replace the ternary battery.
Lithium manganese oxide battery refers to a battery whose positive electrode uses lithium manganese oxide material. The nominal voltage of lithium manganese oxide battery is 2.5~4.2v. Lithium manganese oxide battery is widely used due to its low cost and good safety.
Output voltage range: 2.5~4.2v Nominal capacity: 7500mAh
Standard continuous discharge current: 0.2C
Maximum continuous discharge current: 1C
Working temperature: Charging: 0~45℃
Discharge: -20~60℃
Lead wire model: National standard wire UL3302/26#, wire length 50mm, white wire is 10KNTC
Protection board parameters: (Each parameter can be set according to customer products)
Overcharge protection voltage/each string 4.28±0.025V
Over discharge protection voltage 2.4±0.1V
Overcurrent value: 2~4A
The positive electrode material has low cost, good safety and low temperature performance. However, the material itself is not very stable and easily decomposes to produce gas. Therefore, it is often used in combination with other materials to reduce the cost of the battery cell. However, its cycle life decays quickly, it is prone to swelling, has poor high temperature performance and a relatively short life. It is mainly used for large and medium-sized battery cells. In terms of power batteries, its nominal voltage is 3.7V.
Lithium manganese oxide is mainly spinel-type lithium manganese oxide. Spinel-type lithium manganese oxide LiMn2O4 is a positive electrode material with three-dimensional lithium ion channels first prepared by Hunter in 1981. It has been receiving great attention from many scholars and researchers at home and abroad. As an electrode material, it has the advantages of low price, high potential, environmental friendliness and high safety performance. It is the most promising positive electrode material to replace lithium cobalt oxide LiCoO2 and become a new generation of lithium-ion battery.
Lithium manganese oxide is one of the most promising lithium-ion cathode materials. Compared with traditional cathode materials such as lithium cobalt oxide, lithium manganese oxide has the advantages of abundant resources, low cost, no pollution, good safety, and good rate performance. It is an ideal cathode material for power batteries, but its poor cycle performance and electrochemical stability have greatly limited its industrialization. Lithium manganese oxide mainly includes spinel lithium manganese oxide and layered lithium manganese oxide. Among them, spinel lithium manganese oxide has a stable structure and is easy to achieve industrial production. Today, all products on the market have this structure. Spinel lithium manganese oxide belongs to the cubic crystal system, Fd3m space group, and has a theoretical specific capacity of 148mAh/g. Due to its three-dimensional tunnel structure, lithium ions can be reversibly deintercalated from the spinel lattice without causing structural collapse, so it has excellent rate performance and stability.
Nowadays, the traditional shortcomings of lithium manganese oxide, such as low energy density and poor cycle performance, have been greatly improved (Wanli New Energy typical value: 123mAh/g, 400 times, high cycle type typical value 107mAh/g, 2000 times). Surface modification and doping can effectively modify its electrochemical properties. Surface modification can effectively inhibit the dissolution of manganese and the decomposition of electrolyte. Doping can effectively inhibit the Jahn-Teller effect during charging and discharging. Combining surface modification with doping will undoubtedly further improve the electrochemical properties of the material, and it is believed that it will become one of the directions for future research on the modification of spinel lithium manganese oxide.
LiMn2O4 is a typical ionic crystal with positive and negative configurations. XRD analysis shows that normal spinel LiMn2O4 is a cubic crystal with Fd3m symmetry, unit cell constant a=0.8245nm, unit cell volume V=0.5609nm3. Oxygen ions are face-centered cubic close-packed (ABCABC…., adjacent oxygen octahedrons are connected by common edges), lithium occupies 1/8 oxygen tetrahedral gap (V4) position (lithium is arranged in an orderly manner in the Li0.5Mn2O4 structure: lithium occupies 1/16 oxygen tetrahedral gap in an orderly manner), and manganese occupies 1/2 oxygen octahedral gap (V8) position. There are 56 atoms in the unit lattice: 8 lithium atoms, 16 manganese atoms, and 32 oxygen atoms, of which Mn3+ and Mn4+ each account for 50%. Since the unit cell side length of the spinel structure is twice that of the ordinary face-centered cubic structure (fcc) type, each unit cell is actually composed of 8 cubic units. These eight cubic units can be divided into two types, A and B. Every two cubic units with the same face belong to different types of structures, and every two cubic units with the same edge belong to the same type of structure. Each small cubic unit has four oxygen ions, which are all located at the center from the midpoint of the body diagonal to the vertex, that is, at 1/4 and 3/4 of the body diagonal. Its structure can be simply described as 8 tetrahedral 8a positions are occupied by lithium ions, 16 octahedral positions (16d) are occupied by manganese ions, and the manganese at the 16d position is occupied by Mn3+ and Mn4+ in a 1:1 ratio. The 16c position of the octahedron is all vacant, and the oxygen ions occupy the 32e position of the octahedron. In this structure, the MnO6 oxygen octahedrons are connected by the same edge to form a continuous three-dimensional cubic arrangement, that is, the [M2]O4 spinel structure network provides a three-dimensional empty channel formed by the coplanarity of the tetrahedral lattice 8a, 48f and the octahedral lattice 16c for the diffusion of lithium ions. When lithium ions diffuse in this structure, they diffuse in a straight line along the path of 8a-16c-8a (the energy barrier at the tetrahedron 8a position is lower than the energy barrier at the oxygen octahedron 16c or 16d position), and the angle of the diffusion path is 107°, which is the theoretical basis for using it as a positive electrode material for secondary lithium-ion batteries.
Production of lithium manganese oxide
There are many methods for synthesizing spinel lithium manganese oxide, mainly including high temperature solid phase method, melt impregnation method, microwave synthesis method, sol-gel method, emulsification drying method, coprecipitation method, Pechini method and hydrothermal synthesis method.
There are two main types of lithium manganese oxide on the market today: Class A refers to materials used in power batteries, and its main features are safety and recyclability. Class B refers to alternatives to mobile phone batteries, and its main feature is high capacity.
The production of lithium manganate is mainly based on EMD and lithium carbonate as raw materials, with corresponding additives, and is produced through mixing, sintering, post-processing and other steps. Considering the characteristics of raw materials and production processes, the production itself is non-toxic and environmentally friendly. No wastewater or waste gas is generated, and the powder in production can be recycled. Therefore, it has no impact on the environment.
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