With the development of lithium batteries up to now, the main popular lithium batteries on the market are lithium iron phosphate batteries and ternary lithium batteries. Under such circumstances, which one is better for ternary batteries or lithium iron phosphate batteries? This is a question that many friends who have a demand for batteries need to understand. Let’s see which one is better.
1. In terms of the abundance of raw materials, lithium iron phosphate batteries are more abundant than ternary lithium batteries (containing cobalt, which is a precious and rare mine);
2. In terms of manufacturing costs, lithium iron phosphate batteries are cheaper than ternary lithium batteries, and are more suitable for low-end market demand;
3. The energy density of the ternary lithium battery is higher than that of the lithium iron phosphate battery. Under the same battery space, which lithium battery has the larger capacity;
4. In terms of environmental temperature adaptation and stability, lithium iron phosphate batteries are better than ternary polymer lithium batteries. It can be seen that these two batteries have their own advantages, depending on the environment in which the product is used.
5. In terms of service life, the theoretical value of lithium iron phosphate battery is longer than that of ternary lithium battery;
6. In terms of high temperature resistance, the peak value of lithium iron phosphate electric heating can reach 350℃-500℃, while lithium manganate and lithium sulphate are only around 200℃;
7. In terms of low temperature performance, ternary lithium batteries are better than lithium iron phosphate batteries.
1. Lithium iron phosphate battery
Lithium iron phosphate battery: The raw materials phosphorus and iron are abundant in the earth’s resources, and the supply channels are less restricted. Moderate voltage (3.2V), large capacity per unit weight (170mAh/g), high discharge power, fast charging and long cycle life, and its stability under high temperature and high heat environment is higher than other types of batteries.
Advantages of lithium iron phosphate battery: Compared with the more common ternary lithium phosphate and lithium manganate batteries currently on the market, lithium iron phosphate batteries have at least the following five advantages: higher safety, longer service life, and no Contains rare metals and heavy metals with strong pollution, supports fast charging, and has a wide operating temperature range.
1. Ultra-long life, the cycle life of long-life lead-acid batteries is about 300 times, and the highest is 500 times. The domestically produced lithium iron phosphate power battery has a cycle life of more than 2000 times and is used for standard charging (s hour rate). It can reach 2000 times. Lead-acid batteries of the same quality are new for half a year, old for half a year, and for maintenance and maintenance for half a year, at most 1-15 years, while lithium iron phosphate batteries used under the same conditions will reach 18 years. Comprehensive consideration, the performance-price ratio will be more than: times that of lead-acid batteries.
2. It is safe to use. Lithium iron phosphate completely solves the potential safety hazards of lithium cobalt oxide and lithium manganate.
3. It can be charged and discharged quickly with high current ac. Under the special charger, the battery can be fully charged within 0 minutes after 15c charging, and the starting current can reach c, but the lead-acid battery does not have this performance now.
4. High temperature resistance, the peak value of lithium iron phosphate electric heating can reach 350℃-500℃, while lithium manganate and lithium sulphate are only around 200℃.
5. Large capacity.
6. No memory effect.
7. Green and environmental protection.
Disadvantages of lithium iron phosphate batteries: Lithium iron phosphate has the disadvantages of low tap density and compact density, resulting in poor energy density of lithium-ion batteries; material preparation costs and battery manufacturing costs are high, and battery yields are low.
1. During the sintering process during the preparation of lithium iron phosphate, iron oxide may be reduced to elemental iron in a high-temperature reducing atmosphere. Elemental iron can cause micro-short circuit of the battery, which is the most taboo substance in the battery. This is also the main reason why Japan has not used this material as a positive electrode material for power-type lithium-ion batteries.
2. Lithium iron phosphate has some performance defects, such as low tap density and compaction density, resulting in low energy density of lithium ion batteries. The low temperature performance is poor, even if it is nanometerized and carbon coated, it does not solve this problem. When Dr. Don Hillebrand, director of the Energy Storage System Center of Argonne National Laboratory, talked about the low-temperature performance of lithium iron phosphate batteries, he described it as terrible. Their test results on lithium iron phosphate lithium-ion batteries showed that lithium iron phosphate batteries are at low temperatures. (Below 0°C) It is impossible to drive an electric car. Although some manufacturers claim that the capacity retention rate of lithium iron phosphate batteries is good at low temperatures, that is when the discharge current is small and the discharge cut-off voltage is very low. In this situation, the device cannot start working at all.
3. The cost of material preparation and the manufacturing cost of the battery are relatively high, the battery yield is low, and the consistency is poor. Although the nanometerization and carbon coating of lithium iron phosphate improve the electrochemical performance of the material, it also brings other problems, such as the reduction of energy density, the increase of synthesis cost, poor electrode processing performance, and harsh environmental requirements. Although the chemical elements Li, Fe, and P in lithium iron phosphate are abundant and the cost is low, the cost of the prepared lithium iron phosphate product is not low. Even if the previous research and development costs are removed, the process cost of the material is higher. The cost of preparing the battery will make the final unit energy storage cost higher.
4. Poor product consistency. At present, there is no lithium iron phosphate material factory in China that can solve this problem. From the perspective of material preparation, the synthesis reaction of lithium iron phosphate is a complex multiphase reaction, including solid-phase phosphate, iron oxide and lithium salt, plus carbon precursor and reducing gas phase. In this complex reaction process, it is difficult to ensure the consistency of the reaction.
5. Intellectual property issues. At present, the basic patent of lithium iron phosphate is owned by the University of Texas, while the carbon coating patent is applied by Canadians. These two basic patents cannot be bypassed. If royalties are included in the cost, the cost of the product will be further increased.
Two, ternary lithium battery
Ternary polymer lithium battery: A lithium battery using lithium nickel cobalt manganate (Li (NiCoMn) O2) ternary cathode material as the positive electrode material, specifically refers to the ternary positive electrode and the graphite “ternary power battery” for the negative electrode. The other kind of positive electrode is ternary, and the negative electrode is lithium titanate, which is usually called “lithium titanate”, which is not commonly referred to as “ternary material.”
1. Advantages of ternary lithium battery:
The ternary lithium battery has high energy density and better cycle performance than normal lithium sulphate. 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 sulphate batteries.
The LiNi1/3Co1/3Mn1/3O2 cathode material has a single hexagonal a-NaFeO2 layered rock salt structure similar to LiCoO2, and the spatial 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. Each transition metal atom is surrounded by 6 oxygen atoms to form a MO6 octahedral structure, and 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) and the radius of lithium ions (0.076nm)
It is close, so a small amount of nickel ions may occupy the 3a position, resulting in the occurrence of mixed cations, and this mixed occupation makes the electrochemical performance of the material worse. Usually in XRD, the intensity ratio of the (003)/(104) peak and the splitting degree of the (006)/(012) and (018)/(110) peaks are used as indicators of the cation mixing and occupancy. In general, the intensity ratio of (003)/(104) peak is higher than 1.2, and (006)/
When the peaks of (012) and (018)/(110) split obviously, the layered structure is obvious, and the electrochemical performance of the material is excellent. The unit cell parameters of LiNi1/3Co1/3Mn1/3O2 are a=2.8622A, c=14.2278A. In the crystal lattice, nickel, cobalt, and manganese exist with valences +2, +3, and +4, respectively. At the same time, there are also a small amount of Ni3+ and Mn3+. In the process of charge and discharge, in addition to the electron transfer of Co3+/4+, there are also 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, which have
[v3xV3] Complex model of R30° type superstructure [Ninaco1sMn1] layer, 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 stacking, the lattice formation energy is +0.06eV. Therefore, under appropriate 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 stability of the crystal lattice.
Electrochemical performance and thermal stability of ternary material LiNi1/3Co1/3Mn1/3O2
LiNi1/3Co1/3Mn1/3O2 as a cathode material for lithium-ion batteries has a high lithium ion diffusion capacity and a theoretical capacity of 278mAh/g. During the charging process, there are two platforms between 3.6V and 4.6V. About 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, which is 91% of the 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. At 2.8V～4.3V,
The electrical performance test is carried out in the potential range of 2.8V~4.4V and 2.8V~4.5V, the discharge specific capacity is 159 respectively
mAh/g, 168mAh/g and 177mAh/g are charged and discharged at different temperatures (55°C, 75°C, 95°C) and at different rates of discharge. The structure changes of the material are small, and it has good stability and high temperature performance. Good, but low temperature performance needs to be improved.
The safety of lithium-ion batteries has always been an important measure of commercialization. The thermal effect of the electrolyte with the electrolyte in the charged 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.