Design and property investigations of manganese-based cathode material LiδNi0.25-zMn0.75-zCo2zOy (0 ≤ δ ≤ 1.75) for lithium-ion batteries

Rate Performance Modification of a Lithium-Rich Manganese-Based Material through Surface Self-Doping and Coating Strategies

Lithium-rich manganese-based materials are currently considered to be highly promising cathode materials for next-generation lithium-ion batteries due to their high specific capacity (>250 mA h g^-1) and low cost. A key challenge for the commercialization of these lithium-rich manganese-based materials is their poor rate performance, which is caused by the low electronic conductivity and increasing interface charge transfer resistance produced by the side reaction during the cycling procedure. In this work, we try to improve the rate performance of a lithium-rich manganese-based material Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ using a collaborative approach with Co-doping and Na_xCoO₂-coating methods. Cobalt doping can improve the electronic conductivity, and Na_xCoO₂ coating provides a convenient lithium-ion diffusion channel and moderately alleviates the inevitable decrease in cycling stability caused by cobalt doping. Under the synergistic effect of these two modification strategies, the surface and internal dynamics of the Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ material are enhanced and its rate performance is considerably improved without decay of the cycle stability.

High-Rate Structure-Gradient Ni-Rich Cathode Material for Lithium-Ion Batteries

To simultaneously achieve high compaction density and superior rate performance, a structure-gradient LiNi_0.8Co_0.1Mn_0.1O₂ cathode material composed by a compacted core and an active-plane-exposing shell was designed and synthesized via a secondary co-precipitation method successfully. The tight stacking of primary particles in the core part ensures high compaction density of the material, whereas the exposed active planes, resulting from the stacking of primary nanosheets along the [001] crystal axis predominantly, in the shell region afford enhanced Li⁺ transport. Thus, this structure-gradient Ni-rich cathode material shows a high compaction density with excellent electrochemical performances, especially the rate performance, exhibiting excellent rate capability (160 mA h g^-1 at 10 C), which is 62% larger than that of the pristine material within 2.75-4.3 V (vs Li⁺/Li). Our work proposes a possible strategy for designing and synthesizing layered cathode materials with the required hierarchical structure to meet different application requirements.