facilitate the electrochemical activity of Li 2 MnO 3 . [22][23][24] Conventional approaches in activating Li 2 MnO 3 component in Lirich layered materials are mainly through chemical etching of Li 2 O in Li 2 MnO 3 phases to generate structural defects, such as nitric acid or hydrazine hydrate modifi cation. [ 6,20,25 ] Although Li 2 MnO 3 could be activated, which improved the initial Coulombic effi ciency, the original surface morphology is prone to being destroyed during the etching process ( Figure S1a, Supporting Information), hence leading to the poor cycling stability ( Figure S1b, Supporting Information) and rate performance during subsequent cycles. Li-rich layered materials modifi ed by hydrazine hydrate was reported to have long-term energy retention. [ 20 ] However, the unfavorable platform below 3.0 V appears in the discharge process, which compromises the energy density, especially for the Mn-rich based Li-rich cathode materials ( Figure S2, Supporting Information).Xia and co-workers reported to improve their electrochemical performances through controlled structure defects in Li 2 MnO 3 phase of Li-rich materials. [ 26 ] However, a high degree of structure defects, accompanied with highly disordering of Li + in the transition metal layer, would deteriorate the structural stability, leading to the poor cycling stability and the rate capacity. Na + doping has been reported to be an effective avenue to facilitate the Li + diffusion of Li-rich layered materials and thus to improve their rate capacity. [27][28][29][30] Note that it is vital to control the doping amount of Na + . Li-rich layered materials doped with a low amount of Na + would exhibit the poor cycling stability whereas the material doped with a high amount of Na + shows decreased specifi c capacity and deteriorates the energy density. [ 28 ] Therefore, it is still challenging to develop one simple and effective approach to synthesize Li-rich layered material with much improved kinetics.Herein, we propose a novel method to enhance the kinetics of large particle Li-rich layered materials by gradient surface Na + doping. Driven by Na + concentration diffusion thermodynamically, gradient surface Na + doping are realized through the calcination process of Li-rich materials in molten NaCl state. Powder X-ray diffraction (XRD) shows that high degree of structure defects are formed in Li 2 MnO 3 phase of Li-rich material in molten NaCl fl ux. [ 26 ] Gradient Na + doping on the surface of large particle Li-rich layered material could not only realize the pinning effect in stabilizing the Li-rich layered structure with large amount of structural defects but also facilitate the diffusion of Li + in the layered structure. Accordingly, the resultant large particle Li-rich layered material represents superior electrochemical performances, particularly high specifi c capacity, excellent Coulombic effi ciency, and impressive cycling stability. The schematic illustration of the structural design is shown in Figure 1 .

Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high-capacity electrode materials. According to the concept of energy quality, a high-voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high-capacity Li-rich cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after-treatment, and the specific energy is improved from 912 to 1033 Wh kg . The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.

Self-assembled M-N-doped carbon nanotube aerogels with single-atom catalyst feature are for the first time reported through one-step hydrothermal route and subsequent facile annealing treatment. By taking advantage of the porous nanostructures, 1D nanotubes as well as single-atom catalyst feature, the resultant Fe-N-doped carbon nanotube aerogels exhibit excellent oxygen reduction reaction electrocatalytic performance even better than commercial Pt/C in alkaline solution.