Li Li,Rui Zhao,Tinghua Xu,Dandan Wang,Du Pan,Kun Zhang,Caiyan Yu,Xia Lu,Guanjie He,Ying Bai
LiNi0.5Mn1.5O4 (LNMO) spinel has drawn increasing attention due to its high voltage, stabilized electrochemical performance and safety features as a cathode for lithium-ion batteries. However, the main challenge lies in its unstable surface structure, especially at elevated temperatures. In this paper, we decorate the LNMO precursor with a solid electrolyte of Li1.4Al0.4Ti1.6(PO4)3 (LATP) via a facile sol–gel method, followed by a co-crystallization process at 820 °C, to successfully generate a LATP modification shell at the surface of LNMO. The LATP modification shell could not only optimize the morphology of LNMO including the limitation of particle growth and control of crystalline orientation, but also realize ion doping during the co-crystallization process. By tuning the LATP contents, the 2 wt% LATP modification is found to be the most effective at balancing the interfacial stability and Li+ diffusion kinetics of LNMO, as well as enhancing its rate capability and capacity retention at high temperatures. As a result, the 2 wt% LATP-modified LNMO cathode exhibits a high reversible capacity of 84.8 mA h g−1 after 500 cycles with a capacity retention of 68.9%, and a superior rate capability (102.0 mA h g−1 at 20 C) at room temperature. Moreover, this electrode also delivers a good capacity retention of 85.7% after 100 cycles at 55 °C, which is ascribed to the stabilized interface with a LATP protective layer.
The capacity of Li4Ti5O12 (LTO) at high rates is limited due to the polarization caused by its modest Li-ion (Li+) diffusion coefficient and low electrical conductivity. Coating with ionic conductors is an available method to ameliorate charge transport. Li1+xAlxTi2–x(PO4)3 ion conductors with thermal, chemical, and electrochemical stabilities have been proven to be modification materials for electrodes. Herein, the Li1.4Al0.4Ti1.6(PO4)3 (LATP) precursor dispersion with optimized preparation is applied to the surface modification of LTO by a dynamic mix-drying method. A proper amount of LATP ultrafine particle coating could develop the ion transport rate in the electrode and restrain side reactions. The 2 wt % LATP–LTO anode exhibits an optimized capacity of 168.2 mA h g–1 at 0.1 A g–1 and retains 96.7% of its capacity after 5000 cycles at 5.0 A g–1, while the P-LTO anode retains 86.3% of the capacity. Improved Li+ transport and interface stability in the electrodes lead to the boosted rate and cycling stability. The LATP-modified LTO composites provide a possibility for the further application of related materials in the energy storage field.
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