Preparation And Electrochemical Energy Storage Of Cobalt-manganese-based Oxide Cathode Materials For Potassium/Sodium Ion Batteries

Manganese-based layered oxides as the most competitive cathode materials for potassium-ion batteries（KIBs）.Owing to the large K⁺radius,the de/intercalation of K⁺in the layered structure leads to irreversible structural damage.Therefore,designing manganese-based layered oxides with high stability is crucial for the enhancement of potassium storage performance.Here,the K_0.33Mn O₂·0.18H₂O（KMO-160-10）with high crystallinity and the lowest Mn³⁺content is designed and synthesized.Benefiting from its ultra-stable crystal structure,KMO-160-10 exhibits an initial discharge specific capacity of 116 m Ah g^-1,the capacity remains 50 m Ah g^-1 even at a large current density of 1 A g^-1.This work provides a new viewpoint on the development of cathode materials with higher electrochemical performance for KIBs.In cobalt-based layered oxides for sodium-ion batteries（SIBs）,P2-type cobalt-based layered oxides have open Na⁺diffusion channels but face irreversible structural evolution during charge and discharge process,resulting in poor rate performance.P3-type layered oxides with higher environmental friendliness can be synthesized at lower temperatures,exhibiting higher rate capability but poor cycle stability.Mn-doped cobalt-based layered oxides are designed and synthesized,and the phase composition are tuned successfully by adjusting Mn doping amount.P3-Na_0.28Co_0.48Mn_0.52O₂（NCMO-1）with the optimized stoichiometry exhibits superior rate capability(64 m Ah g^-1 at 3 A g^-1)and promising cycle performance(the capacity remains 58%after 500cycles at 2 A g^-1).The full cell constructed with an NCMO-1 cathode and a HC anode shows competitive energy density of 175.9 Wh kg^-1,demonstrates the feasibility of P3-NCMO-1 as a cathode for SIBs.The sodium content has a great influence on the sodium storage performance.By adjusting the ratio of Na/M（M=Mn,Co）,P3-Na_0.54Co_0.48Mn_0.52O₂（P3-N1）,P2@P3-Na_0.97Co_0.48Mn_0.52O₂（P2@P3-N3）are designed and synthesized.Benefiting from the excellent crystal structure,N1has an ultra-high rate capability(57 m Ah g^-1 at 5 A g^-1);N3 exhibits ultra-long durability after 500 cycles at 3A g^-1.This strategy may open up new opportunities for designing advanced intercalation-type cathode materials for SIBs.