![]() ![]() These parasitic reactions during charging promote unfavourable phase transformations and reduce the thermal stability. Ni 2+ in Ni-based layered oxides tends to migrate to vacancies in the Li layer along the tetrahedral interstice after Li + extraction, accompanied by a loss of lattice oxygen (Fig. This work addresses two key issues of crystal disintegration and interfacial instability of the Ni-rich cathode, and provides adual-modification approach for high-energy cathodes.įailure mechanism and modification design of Ni-rich cathode This strategy is revealed to minimise the capacity sacrifice due to the incorporation of electrochemical inert element. Compared to previously reported single doping or coating modification 9, 10, 11, 12, 13, 14, 15, 16, 23, the simultaneously obtained gradient Al doping inside the primary particles and uniform LiAlO 2 coating on the surface of the secondary particles can concurrently stabilise crystal structure and hinder the parasitic reaction at the interface. In this work, we demonstrate an ultrafast and highly stable performance of synchronous gradient Al-doped and LiAlO 2-coated LiNi 0.9Co 0.1O 2 (NCAl-LAO) cathode materials, which is achieved by an oxalate-assisted deposition method. Up to date, there is no Ni-rich cathode materials can realise a good power and long-term behaviour to satisfy the industry requirements. Because of the sensitivity of the Ni-rich oxide precursor to moisture and air, and abundant Li source (i.e., Li 2CO 3, LiOH) 21, 22, the traditional multistep coating and doping approach is undesirable for industrial production. Theoretical calculations revealed that the doping efficiency is generally low because of easily formed dopant-containing electrochemical inert compounds on the particle surface 19, 20. Because structure disintegration usually commences around the crystal surface 17, 18, and considering the specific capacity, an effective surface-enrichment gradient doping is required for this cathode. Heteroatom doping was applied to stabilise the crystal structure of primary particles with an enhanced Li + diffusivity 15, 16. However, their performance are still far from success because (1) the low Li ionic conductivity coating decreases the specific capacity 11, 12 and (2) the non-uniform coating does not protect the materials well 13, 14. Previous work introduced a surface coating to stabilise the Ni-rich material interface. The cathode–electrolyte interface and the crystal structure must be stabilised simultaneously to obtain a high-power and stable Ni-rich cathode materials. Local heat accumulation under high-rate operation accelerates the transformation from a layered structure to electrochemically inert rock salt phase, which affects the reaction kinetics and capacity deleteriously 10. However, phase transition from H2 to H3 with anisotropic volume deformation yields intergranular and intragranular microcracks, and continuous capacity attenuation of this material 8, 9. To boost the packing density and reduce side reactions with electrolytes, Ni-rich cathode materials may be fabricated as spherical micron-sized secondary particles with nanosized primary particles 7. Layered Ni-rich oxides have been considered promising high-energy and power-dense cathode materials owing to their large theoretical capacity (270 mAh g −1), high output voltage (3.7 V) and rapid ion/electron transfer 4, 5, 6. However, LIBs still experience a “low-energy anxiety” 2, 3. For example, an increased number of people required electronic products to work from home and attend remote conferences, and this phenomenon may be universalised in the post-pandemic era 1. The COVID-19 pandemic has promoted the development of Li-ion batteries (LIBs) globally. A 3.5-Ah pouch cell with the cathode and graphite anode showed more than a 500-long cycle life with only a 5.6% capacity loss. These help the Ni-rich cathode maintain a 97.4% cycle performance after 100 cycles, and a rapid charging ability of 127.7 mAh g −1 at 20 C. The Li +-conductive LiAlO 2 skin prevents electrolyte penetration of the boundaries and reduces side reactions. Theoretical calculations, in situ X-ray diffraction results and finite-element simulation verify that Al 3+ moves to the tetrahedral interstices prior to Ni 2+ that eliminates the Li/Ni disorder and internal structure stress. Here, a synchronous gradient Al-doped and LiAlO 2-coated LiNi 0.9Co 0.1O 2 cathode is designed and prepared by using an oxalate-assisted deposition and subsequent thermally driven diffusion method. Structure combines surface modification is the ultimate choice to overcome these. Critical barriers to layered Ni-rich cathode commercialisation include their rapid capacity fading and thermal runaway from crystal disintegration and their interfacial instability. ![]()
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