Full concentration gradient lithium-rich layered oxides are catching lots of interest as the next generation cathode for lithium-ion batteries due to their high discharge voltage, reduced voltage decay and enhanced rate performance, whereas the high lithium residues on its surface impairs the structure stability and long-term cycle performance. Herein, a facile multifunctional surface modification method is implemented to eliminate surface lithium residues of full concentration gradient lithium-rich layered oxides by a wet chemistry reaction with tetrabutyl titanate and the post-annealing process. It realizes not only a stable Li2TiO3 coating layer with 3D diffusion channels for fast Li+ ions transfer, but also dopes partial Ti4+ ions into the sub-surface region of full concentration gradient lithium-rich layered oxides to further strengthen its crystal structure. Consequently, the modified full concentration gradient lithium-rich layered oxides exhibit improved structure stability, elevated thermal stability with decomposition temperature from 289.57 ℃ to 321.72 ℃, and enhanced cycle performance (205.1 mAh g−1 after 150 cycles) with slowed voltage drop (1.67 mV per cycle). This work proposes a facile and integrated modification method to enhance the comprehensive performance of full concentration gradient lithium-rich layered oxides, which can facilitate its practical application for developing higher energy density lithium-ion batteries.
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Si anode is of paramount importance for advanced energy-dense lithium-ion batteries (LIBs). However, the large volume change as well as stress generates during its lithiation-delithiation process poses a great challenge to the long-term cycling and hindering its application. Herein this work, a composite binder is prepared with a soft component, guar gum (GG), and a rigid linear polymer, anionic polyacrylamide (APAM). Rich hydroxy, carboxyl, and amide groups on the polymer chains not only enable intermolecular crosslinking to form a web-like binder, A2G1, but also realize strong chemical binding as well as physical encapsulating to Si particles. The resultant electrode shows limited thickness change of merely 9% on lithiation and almost recovers its original thickness on delithiation. It demonstrates high reversible capacity of 2104.3 mAh g−1 after 100 cycles at a current density of 1800 mA g−1, and in constant capacity (1000 mAh g−1) test, it also shows a long life of 392 cycles. Therefore, this soft-hard combining web-like binder illustrates its great potential in the future applications.
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One of the bottlenecks limiting the cycling stability of high voltage lithium metal batteries (LMBs) is the lack of suitable electrolytes. Herein, phenyl vinyl sulfone (PVS) is proposed as a multifunctional additive to stabilize both cathode and anode interfaces as it can be preferentially oxidized/reduced on the electrode surfaces. The PVS derived solid electrolyte interphase films can not only reduce the transition metal dissolution on the cathode side, but also suppress the Li dendrite spread on the lithium anode side. The Li||Li symmetric battery with PVS addition delivers longer cycle life and a higher critical current density of over 3.0 mAh cm−2. The LiNi0.8Co0.1Mn0.1O2 (NCM811)||Li full cell exhibits excellent capacity retention of 80.8% or 80.0% after 400 cycles at 0.5 C or 1 C rate with the voltage range of 3.0–4.3 V. In particular, the NCM811||Li cell under constrained conditions remains operation over 150 cycles. This work offers new insights into the electrolyte formulations for the next generation of LMBs.