Synergistic coupling effect of sodium and fluorine co-substitution on enhancing rate capability and cycling performance of Ni-rich cathode for lithium ion battery

Structure and electrochemical performance modulation of a LiNi0.8Co0.1Mn0.1O2 cathode material by anion and cation co-doping for lithium ion batteries

“…However, NCM/CB cathode displays a higher value of Ni 3+ /Ni 2+ (1.35), indicating its ideal stoichiometric composition with less anti-defects. 25,[36][37][38] As shown in Fig. 4c, the O 1s peak at approximately 529.3 eV related to the lattice oxygen in the metal framework.…”

Enhanced Structural Stability and Electrochemical Performance of LiNi0.6Co0.2Mn0.2O2 Cathode Materials by Ga Doping

“…Although impurity phases are not observed in Figure 1 , the research based on synchrotron XRD analysis confirmed the limited solubility of Ga in the LiNiO 2 and the formation of impurity phase Li 5 GaO 4 for the Ga-doped LiNiO 2 samples [ 34 ]. The Li + diffusion coefficient can also be calculated by using the method in reference [ 28 ] to process the EIS data. The obtained Li + diffusion coefficients for the samples with Ga content x = 0, 0.01, 0.02, 0.03, and 0.05 are 1.30 × 10 −12 , 5.80 × 10 −11 , 8.85 × 10 −11 , 6.92 × 10 −11 , and 3.81 × 10 −11 cm 2 s −1 , respectively.…”

“…Because F has strong electronegativity, a more stable crystal structure can be obtained while F ions are doped into the oxygen site of NCM622 material. All of the F-doped samples [ 27 ], including those co-doped with Na and Mg electrode materials [ 28 , 29 ], showed a good rate performance and excellent cycle performance. Recently, the doping and coating of dual functional modified materials prepared by using the same source, such as PO 4 3– gradient doping and Li 3 PO 4 coating dual functional materials [ 30 ], Zr doping and amorphous Li 2 ZrO 3 coating dual functional materials [ 31 ], have also been reported to greatly improve the cycle performance of NCM622 under high temperature and high voltage.…”

Research Progress on Coating and Doping Modification of Nickel Rich Ternary Cathode Materials

“…不同掺杂元素占据的晶格点位有所区别, 而取 代不同点位对 NCM 性能的改善也有所不同。Ta 对 NCM811 的高温(45 ℃)放电比容量和循环性能提 升、电压滞后降低等有益处; Zr、Mg 掺杂时材料的 c 轴变化率更小, 循环性能更佳, 但倍率较差; 使用 Al、Ti、Si 进行掺杂时循环性能也有一定程度的提 高, 但提升效果不如 Ta、Zr、Mg [118] 。必要时, 可 以采用多元素共掺杂的方式。取代 Li 位的 Na 在扩 大锂层层间距的同时, 也有加强结构稳定性的作用, 而掺杂在 O 位的 F 则有利于增强晶型和界面稳定性, 同时进行 Na 和 F 掺杂时, 两者的协同作用能够全面 提升 NCM622 的性能, 如首周库仑效率、倍率、循 环等 [119] 。Mg-Al-B 共掺杂 [120] [121] 。例如, Li 等 [122] 在使用 Zr 对 NCM811 进行掺杂改性时发现, 材料表面会形成一 层 1~2 nm 的 Li 2 ZrO 3 包覆层。 Zr 的掺杂和包覆双重 作用使 NCM811 具有更优的倍率性能和循环性能 [123] 。 由于低镍材料具有更好的稳定性, 因此可以设计内 部富 Ni 表面富 Co、Mn 的梯度材料, 同时提升电性 能和结构性能 [124][125][126] 。有意思的是, 自发形成掺杂/ 包覆双重效果时, 掺杂元素在体相中往往呈梯度分 布, 梯度分布的 Ge 元素能够抑制阳离子混排, 同时 还有利于改善 Li + 离子传输通道 [127] 。阴离子掺杂时 也 有 类 似 效 果 , Ran 等 [128] [70,[129][130][131][132] 。 梯度掺杂还能够在正极材料的表面形成一层无序的 层状结构(图 9), 这种结构比岩盐相更有利于锂离子 的传输, 掺杂元素又进一步提高了氧骨架的坚固性, 形成了特殊的掺杂/包覆结构 [133][134]…”