Radially Microstructural Design of LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Material toward Long-Term Cyclability and High Rate Capability at High Voltage

Abstract

Layered LiNi0.8Co0.1Mn0.1O2 oxide (NCM811) has attracted wide attention as a candidate for the high-energy cathode in lithium-ion batteries (LIBs). It is necessary to amend both the insufficient cycling life caused by microstructural degradation and the poor rate capability due to the restricted kinetics, especially at high voltage. Here we design and synthesize a special NCM811 (R-NCM), containing primary particles arranged radially from the surface to the interior, to address these issues. Compared with the structure of primary particles randomly distributed in conventional NCM811 (C-NCM), this special microstructure in R-NCM shows more reversible cell volume variation, providing more open paths for Li+ transfer, and, more importantly, it significantly alleviates the mechanical stress induced by volume variation inside the particle when cycled to high voltage. Consequently, R-NCM delivers high reversible capacity (221.5 mAh g–1 at a current rate of 0.2 C) and increased rate capability (143 mAh g–1 at a current rate of 10 C) under a cutoff voltage of 4.6 V. Moreover, the long-term cycling stability in R-NCM at 4.6 V is remarkably increased due to the special microstructure. This morphological design provides a method for preparing advanced cathode materials for practical applications.

Relieving the Reaction Heterogeneity at the Subparticle Scale in Ni-Rich Cathode Materials with Boosted Cyclability

“…This special microstructure of S–NCM should be inherited from its precursor, whose flakelike primary grains emanate radially, as shown in Figure S3d–f. The formation of this morphology of S–NCM precursor should be induced by inhibiting the reaggregation process during the initial nucleation process; then, the radial growth of the nanosheet is preferential, which is demonstrated in detail in our previous work …”

Inhibition of Adverse Phase Transition at 4.2 V via increasing Cobalt Content on Ni-Rich Layered Cathode Materials

“…To understand the specific mechanism of cobalt function on Ni-rich layered materials in the cycle process of charge and discharge, it was necessary to start from the Coulomb efficiency of each cycle during charge and discharge. It was previously believed that because of the reaction of oxygen evolution side products with the electrolyte, the material structure began to collapse from the surface, resulting in a gradual decline in the capacity of the material during the cycle process of charging and discharging. , Hence, the comparison of the Coulomb efficiency could explain the effect of modification on the surface structure. Figure b shows the Coulomb efficiency of the prepared samples for 210 cycles.…”

“…It was previously believed that because of the reaction of oxygen evolution side products with the electrolyte, 14 the material structure began to collapse from the surface, resulting in a gradual decline in the capacity of the material during the cycle process of charging and discharging. 30,31 Hence, the comparison of the Coulomb efficiency could explain the effect of modification on the surface structure. Figure 6b shows the Coulomb efficiency of the prepared samples for 210 cycles.…”

Research progress of solid polymer electrolyte/high voltage cathode interphase stability

“…Kim等人 [90] 分别以Li 2 CO 3 和Li 2 CO 3 /LiNbO 3 固溶物作 为涂层包覆NCM622正极, Li 2 CO 3 的分解抑制了CO 2 的 持续生成, NCM622表面能够得到有效稳定. 其中, [82] ; (c) 初生粒子随机生长的C-NCM与初生粒子由中心到表面径向生长的R-NCM的生长机理示意图 [83] (网络版彩图) [89] (网络版彩图) 图 8 富镍NCM正极/聚合物固态电解质界面问题改善. (a) 未包覆NCM622与(b)Li 2 CO 3 包覆NCM622以及(c)Li 2 CO 3 -LiNbO 3 包覆NCM622的SEM图像 [90] ; (d) 未包覆、Li 2 CO 3 包覆和Li 2 CO 3 包覆NCM622循环稳定性 [90] ; (e) 一般聚合物固态电解质和(f) AlF 3 -poly-DOL聚合物固态电解质对集流体的腐蚀示意图 [91] (网络版彩图)…”