January 18, 2021
Comparison of advantages and disadvantages of lithium manganate battery and ternary lithium battery
Lithium manganese oxide batteries and ternary lithium batteries, as members of the lithium battery family, have their advantages and disadvantages. So which is better, lithium manganate battery or ternary lithium battery? This should be compared with their raw materials' advantages and disadvantages after they are made into batteries.
1. The advantages and disadvantages of lithium manganese oxide batteries
The advantages of the manganese acid tank are good rate performance, easier preparation, and lower cost. The disadvantage is that the high-temperature performance and cycle performance are low due to the dissolution of manganese. The high-temperature performance and cycle performance have been greatly improved by doping with aluminum and sintering granulation, which can meet the actual use. In general, lithium manganate batteries have low cost, strong stability, strong low-temperature performance, poor high-temperature performance, and slightly faster attenuation.
There are three types of silver manganate:
(1) Layered lithium manganate LiMnO2, theoretical capacity 285mA-h/g, voltage plateau 4V. The layered structure is challenging to synthesize and unstable, and it is easy to generate Li2Mn204 spinel structure, resulting in a drop in voltage plateau, poor stability, and irreversible capacity degradation.
(2) High voltage spinel lithium manganese oxide LiMn204, theoretical capacity 148mA-h/g, voltage plateau 4.15. Poor high-temperature performance, severe capacity degradation above 55°C. It is also easy to generate Li2Mn204 spinel structure, resulting in a drop in voltage plateau, poor stability, and irreversible capacity degradation. Industrial manganese carp currently uses this type.
(3) Spinel lithium manganese oxide Li2Mn2O4, low voltage (3V), low customer volume, poor circulation is studying how to avoid this kind of thing. Ternary: To solve the defects of layered lithium manganese oxide, through the method of doping metal elements, invented the ternary material LiNiCoMnO2 (LiNiCoAlO2), which is replaced by Ni and Co (Al), which takes into account the high capacity and high voltage of nickel acid buried, The increased pressure and high safety of lithium manganate, the excellent circulation of lithium borate, and at the same time overcome the difficulties and instability of lithium manganate and lithium nickelate synthesis, and the high cost of lithium borate, becoming the current mainstream cathode material. The theoretical capacity is 280mA-h/g, the voltage is 2.7~4.2, and the actual power is about 160mA-h/g.
The positive electrode uses lithium manganese oxide material. So, what is lithium manganate? It is produced from EMD (a raw material used as a unique material for mercury-free alkaline manganese batteries) and lithium carbonate (also a raw material), with corresponding additives, through mixing and sintering steps.
When we talk about active lithium, we say that it has a spinel structure, which refers to the crystal shape used in lithium batteries. When lithium manganate is not used in lithium batteries, it has a layered structure. The spinel structure is more stable than the layered structure (although based on chemical properties, it seems that the stability of different shapes in geometry can also be thought of), so the spinel structure is still used in practical applications. In addition to lithium manganese oxide, lithium drill oxide and ternary lithium battery positive electrodes are also spinel structures. Nevertheless, lithium manganese oxide's spinel structure is very distinctive compared to its two counterparts: both advantages and disadvantages. Very prominent. Its benefits are low-temperature resistance, good rate performance, and relatively easy preparation. The disadvantages are: the material itself is unstable and needs to be mixed with other materials, poor high-temperature performance, poor cycle performance, and fast attenuation. These shortcomings of lithium manganate come from the characteristics of manganese. However, due to the widespread existence of manganese, it has obvious cost advantages.
Because the lithium manganese oxide material has such distinctive characteristics, people can use its advantages and suppress its shortcomings to make the lithium manganese acid battery be used in different fields, usually referred to as two applications of type A and type B. Type A refers to power batteries, with emphasis on safety and cycle performance, and requires a reversible capacity of 100~115mAh/g, which can maintain 80% capacity after 500 cycles. Type B is mainly used in consumer electronics (mobile phones), characterized by a high degree. The general requirement is that the reversible capacity is 120mAh/g, but the cycle performance only requires that the power be maintained 60% after 300 to 500 times.
2, the advantages and disadvantages of ternary lithium batteries
Ternary battery, ternary polymer battery or ternary polymer lithium battery, etc., refer to the ternary lithium battery; what is ternary lithium battery? This is to talk about the ternary material LiNi1/3Co1/3Mn1/302 used to manufacture ternary lithium batteries.
(1) Advantages of ternary lithium battery:
The ternary lithium battery has high energy density and better cycle performance than standard lithium sulfate. At present, with the continuous improvement of the formula and the perfect structure, the nominal voltage of the battery has reached 3.7V, and the capacity has reached or exceeded the level of lithium sulfate batteries.
LiNi1/3Co1/3Mn1/3O2 cathode material has a single hexagonal a-NaFeO2 layered rock salt structure similar to the LiCoO2 space point group is R3m. Lithium ions occupy position 3a of the (111) plane of the rock salt structure, transition metal ions occupy position 3b, and oxygen ions occupy position 6c. Six oxygen atoms surround each transition metal atom to form a MO6 octahedral structure, while lithium ions are inserted into transition metal atoms. Ni1/3Co1/3Mn1/3O layer formed with oxygen. Because the radius of divalent nickel ions (0.069nm) is close to that of lithium ions (0.076nm), a small number of nickel ions may occupy the 3a position, leading to the occurrence of mixed cations, and this mixed occupancy makes the material The electrochemical performance becomes worse. Usually, in XRD, the intensity ratio of the (003)/(104) peak and the splitting degree of the (006)/(012) and (018)/(110) flowers are used as indicators of the cation mixing and occupation. In general, when the intensity ratio of (003)/(104) height is higher than 1.2, and the (006)/(012) and (018)/(110) flowers are split, the layered structure is apparent, and the electrochemical properties of the material Excellent performance. The unit cell parameters of LiNi1/3Co1/3Mn1/3O2 are a=2.8622A, c=14.2278A. Nickel, cobalt, and manganese exist in the crystal lattice with valences +2, +3, and +4, respectively. At the same time, there is also a small amount of Ni3+ and Mn3+. In charge and discharge, and the electron transfer of Co3+/4+, the electron transfer between Ni2+/3+ and Ni3+ also makes the material have a higher specific capacity. Mn4+ only serves as a structural substance and does not participate in the redox reaction. Koyama et al. proposed two models describing the crystal structure of LiNi1sCou3Mnm3O2, namely, a complex model with [v3xV3] R30° type superstructure [Ninaco1sMn1] layer, and the unit cell parameter a=4.904
A.c=13.884A. The lattice formation energy is -0.17eV, and the simple model of CoO2, NiO2, and MnO2 layer orderly accumulation, the lattice formation energy are +0.06eV. Therefore, under suitable synthesis conditions, the first model can be formed. This crystal type can minimize the change in the volume of the crystal lattice and reduce the energy during the charge and discharge process, which is beneficial to the crystal lattice's stability.
The electrochemical performance and thermal stability of the ternary material LiNi1/3Co1/3Mn1/3O2 LiNi1/3Co1/3Mn1/3O2 cathode material of the lithium-ion battery has a high lithium-ion diffusion capacity, and the theoretical capacity is 278mAh/g. In the process, there are two platforms between 3.6V and 4.6V; one is around 3.8V, the other is about 4.5V, mainly due to the two electric pairs of Ni2+/Ni4+ and Co3+/Co4+, and the capacity can reach 250mAh/s is 91% of theoretical capacity. In the voltage range of 2.3V~4.6V, the discharge specific capacity is 190mAh/g; after 100 cycles, the reversible specific capacity is more than 190mAh/g. The electrical performance test is carried out in the potential range of 2.8V～4.3V, 2.8V～4.4V, and 2.8V～4.5V. The specific discharge capacity is 159mAh/g, 168mAh/g, and 177mAh/g, respectively. Under different temperatures (55℃, 75°C, 95°C) and different rates of charge and discharge, the material structure changes are small, have good stability, high-temperature performance is good. Still, low-temperature performance needs to be improved.
The safety of lithium-ion batteries has always been an essential measure of commercialization. The electrolyte's thermal effect with the charging state is the key to whether the cathode material is suitable for lithium-ion batteries.
DSC test results show that the charged LiNi1gCo1gMn1/3O2 has no peak at 250~350℃, LiCoO2 has two exothermic peaks at 160℃ and 210℃, and LiNiO2 has an exothermic peak at 210℃. Ternary materials also have some exothermic and endothermic reactions in this temperature range, but the reaction is much milder.
(2) Disadvantages of ternary lithium battery:
Ternary material power lithium batteries mainly include nickel diamond lithium aluminate batteries, nickel diamond lithium manganate batteries, etc. The high-temperature structure is unstable, resulting in poor high-temperature safety, and too high pH can easily cause the monomer to swell and cause malfunctions. Current conditions The cost is not low.