Boosting the Electrochemical Performance of Li-and Mn-Rich Cathodes by a Three-in-One Strategy

There are plenty of issues need to be solved before the practi-cal application of Li-and Mn-rich cathodes,including the detrimental voltage decay and mediocre rate capability,etc.Element doping can e ectively solve the above problems,but cause the loss of capacity.The introduction of appropriate defects can compensate the capacity loss;however,it will lead to structural mismatch and stress accumulation.Herein,a three-in-one method that combines cation–polyanion co-doping,defect construction,and stress engineering is pro-posed.The co-doped Na^(+)/SO_(4)^(2-)can stabilize the layer framework and enhance the capacity and voltage stability.The induced defects would activate more reac-tion sites and promote the electrochemical performance.Meanwhile,the unique alternately distributed defect bands and crystal bands structure can alleviate the stress accumulation caused by changes of cell parameters upon cycling.Consequently,the modified sample retains a capacity of 273 mAh g^(-1)with a high-capacity retention of 94.1%after 100 cycles at 0.2 C,and 152 mAh g^(-1)after 1000 cycles at 2 C,the corresponding voltage attenuation is less than 0.907 mV per cycle.

Mechanisms and applications of layer/spinel phase transition in Li-and Mn-rich cathodes for lithium-ion batteries

Li-and Mn-rich(LMR)cathode materials have received tremendous attention due to the highly reversible specific capacity(>250 m Ah·g^(-1)).In the analysis of its crystal structure,the two-phase composite model gains increasing acceptance,and the phase transition behaviors in LMR cathode materials have been extensively studied.Herein,the structure controversy of LMR cathode materials,and the mechanisms of phase transition are summarized.Particularly,the causes of initiating or accelerating the phase transition of LMR cathode materials have been summarized into three main driving forces,i.e.,the electrochemical driving force,the component driving force and the thermodynamic driving force.Additionally,the applications of phase transition behavior in improving the electrochemical performance of LMR cathode materials,including the construction of spinel surface coating and spinel/layered hetero-structure are discussed.