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Layered Li-rich 3d-transition-metal cathode materials, xLi 2 MnO 3 •(1−x)LiMO 2 , have increasingly triggered immense interest for their use in Li-ion batteries due to their advantages in terms of energy density. Nevertheless, poor cycle and rate performances cause limitations in practical commercial applications. We modified the material with boron bulk doping and carbon surface modification to form a B-doped layered@spinel@carbon heterostructure. Herein, B-doping can increase the lattice spacing favorable for Li + insertion/extraction and inhibit oxygen loss successfully. The spinel layer and carbon on the surface can protect the material from corrosion due to electrolyte decomposition, which can accelerate Li + and electron conduction and lessen the phase transition. The co-modified material reveals outstanding cycle and rate capability. Especially, it not only shows superior thermal stability at the high temperature of 45 °C, with a capacity retention rate of 83.3%, but also shows a higher discharge capacity of 108.9 mAh g −1 at the low temperature of −20 °C. Furthermore, the mechanism of the Li-rich cathode material with improved performance was also detected systematically. The proposed facile synthesis and co-modification of the boron-doped layered@spinel@carbon heterostructure can shed light on the design direction for cathode materials of lithium-ion batteries to solve the problem of electrochemical performance degradation caused by structural instability.

The low‐concentration electrolyte possesses the benefits of desirable wettability, low viscosity, and low cost. However, the mechanism of its poor electrochemical performance is not clear. Herein, the properties of interfacial films on the surface of LiFePO4 (LFP) cathode material formed by electrolytes with different concentrations are compared by interfacial component analysis. It is shown that moderate content of lithium fluoride increases the length of Li+–ethylene carbonate bond from 1.676 to 1.824 Å through lithium bond and then decreases the desolvation activity energy of Li+ ion, which effectively promotes the desolvation process of Li+ ion at the interface of LFP/electrolyte, and finally ensures the perfect performance of the battery. That is, the fundamental cause for the undesirable electrochemical performances of the low‐concentration electrolyte is the low content of LiF components in the interface film rather than the low ionic conductivity of the electrolyte itself. This indicates the direction of optimizing the electrochemical performance of low‐concentration electrolytes.

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