Currently, achieving high capacity energy density and power density has become the focus of expanding Lithium batteries applications to large-scale energy storage systems. Therefore, high load level and harsh calendering process are needed in the electrode manufacturing process to meet the requirements of high volume energy density of batteries.
Although the electrode fabrication process is highly optimized to regulate electron and ion transport on the electrode, local ion diversity and electron conductivity eventually lead to severe reaction heterogeneity, which affects the stability of the battery. Under specific manufacturing conditions and operating environment, this heterogeneous reaction behavior becomes intense. In addition, the serious microstructure collapse of the surface particles in the rolling process may cause local deviation in the long-term cycling process.
At the same time, nickel based LiNixCoyMnzO2(NCM), as a candidate material for high-energy cathode electrode, is particularly fragile in maintaining the integrity of the particles due to the polycrystalline aggregates of secondary particles. In the rolling process, under the action of high pressure, the mechanical fracture particles on the surface of the electrode will cause a higher surface reaction, and the local structure and composition will change with the change of the electrode depth. Therefore, the preferential reaction on the positive side will significantly deteriorate the integrity of the positive pole and the uneven consumption of circulating lithium in the whole battery. Unfortunately, this critical defect associated with the intrinsic morphological characteristics of NCM particles is rarely addressed systematically. Therefore, in order to improve the performance of the battery, it is necessary to fully understand the NCM material at the electrode level.
The researchers found that nickel-rich materials tend to decay in the longitudinal direction due to their highly unstable chemical and mechanical properties. The decaying behavior is due to the excessive use of surfactant, which results in the seriously uneven distribution of potential in the long-term cycle. At the same time, continuous degradation reduces the reversibility of lithium ions.
Here, the researchers suggest that robust single crystal Lini0.8Co0.1Mn0.1O2 be used as a feasible alternative material, so as to effectively inhibit the local excessive utilization of the active material. The electrochemical performance of high energy lithium ion battery can be stabilized by this method. After 1000 cycles at 45℃, the battery capacity can be kept above 80%.
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