Modulating the discharge capacity and cycling performance of the LiMn0.6Fe0.4PO4 cathode for lithium-ion batteries via titanium introduction †
Abstract
LiMn0.6Fe0.4PO4 has garnered considerable attention due to its higher operating voltage and theoretical energy density in comparison to the commercial LiFePO4. However, LiMn0.6Fe0.4PO4 still encounters challenges of discharge capacity and cycling performance. To address these issues, Ti doping is implemented through a scalable solid-state method to substitute the Mn site in the LiMn0.6Fe0.4PO4 crystal structure. LiMn0.57Ti0.03Fe0.4PO4 exhibits superior specific capacities of 151.4 and 139.3 mAh g−1 at 0.2 and 1C, respectively, with an impressive capacity retention rate of 87.4% after 500 cycles at 1C. It is found that the lithium-ion diffusion channel is broadened and the lithium-ion diffusion rate is enhanced (∼10−12 S cm−1) by a combination of structural and electrochemical studies. Interestingly, lithium-ion diffusion ability is greatly improved during the Mn2+/Mn3+ than the Fe2+/Fe3+ couple. Moreover, the electronic conductivity has also been enhanced. Furthermore, structure stability between LixMn0.6Fe0.4PO4 and Mn0.6Fe0.4PO4 phases is dramatically boosted during delithiation/lithiation. This study elucidates the comprehensive mechanism of the role of Ti doping and opens up new technology space to improve the discharge capacity and cycling performance of lithium-ion batteries.