Distinctive electrochemical performance of novel Fe-based Li-rich cathode material prepared by molten salt method for lithium-ion batteries

For constructing next-generation lithium-ion batteries with advanced performances, pursuit of high-capacity Li-rich cathodes has caused considerable attention. So far, the low discharge specific capacity and serious capacity fading are strangling the development of Fe-based Li-rich materials. To activate the extra-capacity of Fe-based Li-rich cathode materials, a facile molten salt method is exploited using an alkaline mixture of LiOH–LiNO₃–Li₂O₂ in this work. The prepared Li_1.09(Fe_0.2Ni_0.3Mn_0.5)_0.91O₂ material yields high discharge specific capacity and good cycling stability. The discharge specific capacity shows an upward tendency at 0.1 C. After 60 cycles, a high reversible specific capacity of ∼250 mAh g⁻¹ is delivered. The redox of Fe³⁺/Fe⁴⁺ and Mn³⁺/Mn⁴⁺ are gradually activated during cycling. Notably, the redox reaction of Fe²⁺/Fe³⁺ can be observed reversibly below 2 V, which is quite different from the material prepared by a traditional co-precipitation method. The stable morphology of fine nanoparticles (100–300 nm) is considered benefiting for the distinctive electrochemical performances of Li_1.09(Fe_0.2Ni_0.3Mn_0.5)_0.91O₂. This study demonstrates that molten salt method is an inexpensive and effective approach to activate the extra capacity of Fe-based Li-rich cathode material for high-performance lithium-ion batteries.