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Author ：Iflowpower – Portable Power Station Supplier
With the rapid development of new energy vehicles, more and more electric vehicles began to enter the life of ordinary consumers, there are two points on electric vehicles concerned: 1) Endurance mileage, this important and lithium-ion battery Energy density is related; 2) service life, this important and lithium-ion battery's cycle life. In recent years, with the continuous improvement of the battery life, the energy density of the power lithium battery is also continuous, but a negative impact brought by high energy density is the decline in cycle life, which seems to be a power lithium battery can't escape. A fate, but the single crystal material that appeared in recent years seems to have a long-term road to the long life of high energy density lithium-ion batteries.
2017 JINGLI (First Server) and JRDAHN (Croatient author) in Darhaus in 2017, the performance performance of single crystal NCM523 and polycrystalline NCM523 materials in soft bag lithium battery, studies have shown that single crystal NCM523 materials are more suitable for applications in areas with high circulating life. Although the secondary particles have a diameter of 10 um or more, the size of the primary particles is only 200-400 nm, and the single particle diameter of the single crystal NCM523 material is about 2-3 um (as shown in the figure). It is much larger than the size of the polycrystalline NCM523 primary crystal particles.
The figure below shows the scanning electron micrograph of the single crystal NCM 523 material particles, which can see a small number of larger particles in the single crystal NCM 523 material in the figure, consisting of a plurality of crystal particles, and the particles are constituted by a single crystal. The following figure shows single crystal NCM523 (SC-523) and polycrystalline NCM523 (UC-523), and Al2O3 coated NCM523 (AC-523) three materials in the buckle semi-battery in 3-4.5V, 3-4.
4V. And the charge and discharge curve within the 3-4.3V voltage range, the current density is 10 mA / g (C / 20), the test temperature is 30 ¡ã C.
The table below is the specific capacity data of the three materials at 4.3V, 4.4V and 4.
5V cutoff voltage. From the figure below, the reversible capacity of the AC-523 material is highest in each voltage, and can reach 174.6, respectively.
MAH / G, 188.1MAH / g and 199.2mAh / g, and the specific capacity of single crystal NCM523 material is 165.
6, 179.2 and 189.9mAh / g, respectively, and is the lowest in three materials.
The following figure shows the three-material and graphite negative electrode produced soft bag lithium battery with a change in the number of cycles, the test conditions are 3-4.4V, the temperature is 40 ¡ã C, which uses different electrolyte additives, respectively, from the following figure It can be seen in the electrolytic solution in which electrolyte NCM 523 is used to be significantly better than the polycrystalline NCM523 material, which also indicates that the interface stability of the single crystal material is better, and the occurrence of side reactions can be reduced. In order to further verify the interfacial stability of the single crystal NCM 523 and Al2O3 surface covering NCM523 materials, the authors use PES211 electrolyte, graphite negatives to make soft-boiled lithium batteries, which are floating at 4.
4 V, 4.5V and 4.6V and 40 ¡ã C, respectively.
100h, respectively. It can be seen from the following figure to see that the single crystal NCM523 material is very small in the entire floating process, from 0.01, 0.
01 and 0.04ml, and the polycrystalline NCM523 material, although the surface is covered with Al2O3, but the volume of the gas produced is still Up to 0.07, 0.
27 and 0.62 ml, the experiment shows that the single crystal NCM523 material can inhibit the occurrence of side reactions, thereby reducing the gas gas at high voltages. The figure below shows the test results of the introduction of O2 when heating in different SOC states, and can see the polycrystalline NCM523 material in the vicinity of the polycrystalline NCM523 material in 80 ¡ã C, especially in high This peak change in the SOC state is more obvious, while single crystal NCM523 materials do not have release O2 peaks at this temperature.
The three materials can be seen from the following picture AC also have a peak in the range of 200-350 ¡ã C. As the SOC has improved, the strength of the peak has also increased, although three materials are in this O2 release peaks have an O2 release peak, but the peak temperature of single crystal material is the highest, which also indicates that the single crystal NCM523 material is more excellent in thermal stability than conventional polycrystalline NCM 523. The figure below shows that the single crystal NCM 523 and the polycrystalline NCM 523 and the graphite prepared by the graphite use different electrolytes to compare cycle properties (C / 2, 3-4.
4V) comparison at 40 and 55 ¡ã C, from the following figure, At 40 ¡ã C, still at 55 ¡ã C, the cycle performance of the single crystal NCM523 material is significantly better than the Al2O3 coated NCM 523 material, such as single crystal NCM523 battery of Q2FEC and PES211 electrolyte at 40 ¡ã C, 300 times After the cycle, the capacity retention ratio can still reach 98%, while the battery of the Al2O3 coated NCM523 material is only 92% of the capacity retention ratio of 300 times in the case of the same electrolyte, which is more than 55 ¡ã C. Obviously, a single crystal NCM523 material battery of PES211, Q5FEC and 1BFC electrolyte is 300 times, and the capacity retention ratio of more than 94%, while the capacity retention ratio of the AL2O3 coated NCM523 material battery is less than 85%. In general, the single crystal NCM523 material is lower than the polycrystalline NCM 523 material, but in the gas, thermal stability, especially in the circulating performance, single crystal NCM523 material is significantly better than the polycrystalline NCM523 material.
Therefore, the single crystal NCM523 material is more suitable for applications in some of the multivary performance requirements, but there is a high-demanding area for cycle pe.
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