Lithium Deficiencies Engineering in Li-Rich Layered Oxide Li_1.098Mn_0.533Ni_0.113Co_0.138O₂ for High-Stability Cathode

Abstract

Li-rich layered oxides have been in focus because of their high specific capacity. However, they usually suffer from poor kinetics, severe voltage decay, and capacity fading. Herein, a long-neglected Li-deficient method is demonstrated to address these problems by simply reducing the lithium content. Appropriate lithium vacancies can improve dynamics features and induce in situ surface spinel coating and nickel doping in the bulk. Therefore, the elaborately designed Li 1.098 Mn 0.533 Ni 0.113 Co 0.138 O 2 cathode possesses improved initial Coulombic efficiency, excellent rate capability, largely suppressed voltage decay, and outstanding long-term cycling stability. Specifically, it shows a superior capacity retention of 93.1% after 500 cycles at 1 C (250 mA g −1 ) with respect to the initial discharge capacity (193.9 mA h g −1 ), and the average voltage still exceeds 3.1 V. In addition, the discharge capacity at 10 C can be as high as 132.9 mA h g −1 . More importantly, a Li-deficient cathode can also serve as a prototype for further performance enhancement, as there are plenty of vacancies.

Function and Application of Defect Chemistry in High‐Capacity Electrode Materials for Li‐Based Batteries

“…Our group has introduced the cathodic Li vacancies by a solid-state method and verified their functional sites in LRMC cathode materials. [5] Different from the vacancies, the heteroatoms doping belongs to the extrinsic defects, which is caused by the foreign atoms replacing the original atoms in one of the lattice points. If the foreign atom has a different charge to the replaced atom, another vacancies or gap atoms would be generated, and the replaced atom needs to gain or lose electrons to achieve charge balance.…”

“…[27] Except for O vacancies, appropriate Li vacancies are benefiting to reduce the energy barrier of Li-ion diffusion, enhance the utilization of Li-ion and in situ induce Ni-ion doping, thus improving the Li storage properties. [5] Vacancy engineering applied in sulfur cathodes can boost their electrical conductivity of sulfur hosts and the formation of S 3 À radicals. When metal compounds such as TiO 2 and MoS 2 as sulfur hosts contain the vacancies, their electrons below the Fermi level can leap into the defect level, which would create a hole carrier and lower the barrier of electron transition to the conduction band, resulting in the improvement of the electronic conductivity and the acceleration of the lithium polysulfides (LiPSs) conversion reaction kinetics.…”

“…The element ratio of Li/TM of LLLO (~1.400) is lower than that of the PLLO (~1.676), indicating the presence of Li vacnacies in the LLLO. [5] Lattice doping. Doping can effectively enhance the structural stability and promote the Li-ion diffusion, being beneficial to improve the electrochemical behavior of LRCM.…”

“…[4] In our early work, Li vacancies and Ni heteroatoms are introduced into LRMC materials, which can reduce the Li-ion diffusion barrier and forbid the over oxidation of lattice oxygen. [5] So far, the researches about how to construct defects and exploring the benefits to batteries have attracted more concern, and the understanding of defect theories is becoming clearer.…”

Surface Architecture Design of LiNi0.8Co0.15Al0.05O2 Cathode with Synergistic Organics Encapsulation to Enhance Electrochemical Stability

“…Among different types of Ni‐rich cathode materials for LIBs, LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) has been considered to be one of the most attractive cathode materials. Unfortunately, like other Ni‐rich cathode materials, NCA cathode materials suffer from rapid capacity decline, [11–13] which can be attributed to its structural instability during charge/discharge cycles mainly caused by Li + /Ni 2+ disorder, surface reactions arising from accumulation of a NiO‐like phase on the surface of the cathode material, oxygen release that destabilizes the crystal structure, and corrosion of active materials resulting from interfacial contact between electrolyte and active material [14–18] …”