Experiments and theoretical calculations reveal that the additional capacity originates from additional lithium ion storage on the reconstructed LFP surface through C-O-Fe bonds, which can be obtained by compensating the broken symmetry of surface Fe to obtain two additional lithium ions on the reconstructed surface. storage sites to enhance the binding energy of surface lithium. This overcapacity phenomenon is found in both LiFe1-xMnxPO4 (0≤x≤1) and LiFe1-xCoxPO4 (0≤x≤1) materials.

　　【introduction】

　　The high capacity and high rate performance of lithium-ion batteries depend on the development of new cathode materials and structural improvements. The nanocrystal benefits from its shorter lithium ion diffusion path, enhancing the dynamic properties of LiMPO-4-(M=Fe,Mn,Co).

　　However, the use of LiMPO-4-nanocrystals in batteries also has a number of disadvantages compared to bulk materials. For example, the incompleteness of the crystal surface will cause the lithium ions at the interface to have lower binding energy, resulting in a reduction in charge and discharge voltage and a loss of capacity; at the same time, a large specific surface area will generate more active sites, The problem of transition metal cation dissolution will become more obvious, which is also the main factor affecting the charge and discharge stability of lithium batteries. Secondly, the reduction in tap density and energy density caused by nanotechnology is a problem that cannot be ignored in industrial production.

　　【Achievements Introduction】

　　Recently, Professor Pan Feng from Peking University Shenzhen Graduate School published an article titled "ExcessLi-IonStorageonReconstructedSurfacesofNanocrystalsToBoostBatteryPerformance" in the famous journal NanoLetters. This article reports a surface reconstruction method to reduce defects in LFP nanocrystals, thereby improving the capacity and rate performance of lithium-ion batteries. Through unique surface reconstruction, LFP nanocrystals exhibit supercapacity performance with size effect. LFPs with average particle sizes of 83nm and 42nm can exhibit specific capacities of 186 and 207mAhg-1 (exceeding the theoretical value of 170mAhg-1 by 9.4% and 21.8%, respectively). Moreover, the composite electrode based on LFP nanocrystals shows good cycle stability and high rate characteristics. The capacity loss after 1000 cycles at 10C current density is only 0.3-1.1%, and the electrode can still show 114mAhg-1/127mAhg at 50C rate. -1 charge/discharge capacity. Experiments and theoretical calculations reveal that the additional capacity originates from additional lithium ion storage on the reconstructed LFP surface through C-O-Fe bonds, which can be obtained by compensating the broken symmetry of surface Fe to obtain two additional lithium ions on the reconstructed surface. storage sites to enhance the binding energy of surface lithium. This overcapacity phenomenon is found in both LiFe1-xMnxPO4 (0≤x≤1) and LiFe1-xCoxPO4 (0≤x≤1) materials.

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