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[Display omitted] Benefiting from the extra contribution of O redox, Co-free Li-rich layered oxides (LRNMO) can satisfy the requirement of high specific capacities. However, during the high-voltage charging process, lattice oxygen being oxidized to O− or O 2 leads to a gradual transition of the structure from layered to spinel phase, capacity and voltage decline, hindering the practical application of LRNMO in the lithium-ion battery. Here, a surface modification strategy of Li 1.2 Ni 0.32 Mn 0.48 O 2-δ doped with Ta5+ ions is proposed, in which the Ta5+ ions occupy the lithium sites of the lattice structure on the surface layer of LRNMO and form a Ta 2 O 5 coating layer. The modified electrode exhibits excellent rate performance and cycling stability, with 94.9% and 85.5% capacity retention rate and voltage retention rate, respectively, after 200 cycles at 1C. Moreover, the initial coulomb efficiency and ionic conductivity of the modified electrode are also apparently enhanced. Simultaneously, the decreased Li/Ni mixing degree of the modified electrode reflects the improvement of the structural stability. Therefore, the modification strategy through strong metal–oxygen bonding to integrate the surface structure to regulate the oxygen activity provides a new direction for the design of high energy density Co-free Li-rich cathode materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Benefiting from the extra contribution of O redox, Co-free Li-rich layered oxides (LRNMO) can satisfy the requirement of high specific capacities. However, during the high-voltage charging process, lattice oxygen being oxidized to O− or O 2 leads to a gradual transition of the structure from layered to spinel phase, capacity and voltage decline, hindering the practical application of LRNMO in the lithium-ion battery. Here, a surface modification strategy of Li 1.2 Ni 0.32 Mn 0.48 O 2-δ doped with Ta5+ ions is proposed, in which the Ta5+ ions occupy the lithium sites of the lattice structure on the surface layer of LRNMO and form a Ta 2 O 5 coating layer. The modified electrode exhibits excellent rate performance and cycling stability, with 94.9% and 85.5% capacity retention rate and voltage retention rate, respectively, after 200 cycles at 1C. Moreover, the initial coulomb efficiency and ionic conductivity of the modified electrode are also apparently enhanced. Simultaneously, the decreased Li/Ni mixing degree of the modified electrode reflects the improvement of the structural stability. Therefore, the modification strategy through strong metal–oxygen bonding to integrate the surface structure to regulate the oxygen activity provides a new direction for the design of high energy density Co-free Li-rich cathode materials. [ABSTRACT FROM AUTHOR]

Li-rich Mn-based cathode materials are one kind of the promising potential candidates to electric vehicles powered by high-energy density lithium-ion batteries due to its much higher theoretical energy density. Unfortunately, the rapid capacity fading and voltage decay are the most critical factors affecting its practical application. Herein, Li 1 · 17 Na 0 · 02 Mn 0 · 54 Ni 0 · 13 Co 0 · 13 O 2 (PN-LMNCO) is prepared via surface phase structure controlling and ion doping through an architecture strategy of surface lithium deficiency. It is found that the existence of lithium deficiencies can induce surface phase transformation, and thus resulting in an in-situ spinel surface conversion film, which can restrain the structure degradation during subsequent charge/discharge process. In addition, because of the larger ion radius than Li+, Na+ doping can effectively increase the spacing between Li layers, and thus improve the rate capacity. Accordingly, the as-prepared sample displays as a significantly higher initial coulombic efficiency (91.2%). After 200 cycles at 1 C, the PN-LMNCO can retain 94.7% discharge specific capacity. Furthermore, PN-LMNCO can still show a good discharge capacity of 214 mA h g−1 even at a high current rate of 5 C. Therefore, this work can preferably meet the need of the development of electric vehicle for high-energy density Lithium-ion battery. • Lithium deficiencies induce the in-situ spinel surface conversion film. • The interfacial reaction has been inhibited. • Na doping improves the diffusion kinetics of lithium ions. • There are any redundant synthesis steps and the cost be reduced. [ABSTRACT FROM AUTHOR]