Enhancing mechanical properties of composite solid electrolyte by ultra-high molecular weight polymers.

Composite solid electrolytes combining the advantages of inorganic and polymer electrolytes are considered as one of the promising candidates for solid-state lithium metal batteries. Compared with ceramic-in-polymer electrolyte, polymer-in-ceramic electrolyte displays excellent mechanical strength to inhibit lithium dendrite. However, polymer-in-ceramic electrolyte faces the challenges of lack of flexibility and severely blocked Li+transport. In this study, we prepared polymer-in-ceramic film utilizing ultra-high molecular weight polymers and ceramic particles to combine flexibility and mechanical strength. Meanwhile, the ionic conductivity of polymer-in-ceramic electrolytes was improved by adding excess lithium salt in polymer matrix to form polymer-in-salt structure. The obtained film shows high stiffness (10.5 MPa), acceptable ionic conductivity (0.18 mS cm-1) and high flexibility. As a result, the corresponding lithium symmetric cell stably cycles over 800 h and the corresponding LiFePO4cell provides a discharge capacity of 147.7 mAh g-1at 0.1 C without obvious capacity decay after 145 cycles.

Synthesizing high performance LNMO cathode materials with porous structure by manipulating reynolds number in a microreactor.

The demand for Lithium-ion batteries (LIBs) has significantly grown in the last decade due to their extensive use electric vehicles. To further advance the commercialization of LIBs for various applications, there is a pressing need to develop electrode materials with enhanced performance. The porous microsphere morphology LiNixMn2-xO4(LNMO) is considered to be an effective material with both high energy density and excellent rate performance. Nevertheless, LNMO synthesis technology still has problem such as long reaction time, high energy consumption and environmental pollution. Herein, LNMO microsphere was successfully synthesized with short precursors reaction time (18 s) at 40 °C without using chelating agent by microreaction technology combined solid-state lithiation. The optimized LNMO cathode shows microsphere (∼8µm) morphology stacked by nano primary particles, with abundant mesoporous and fully exposed low-energy plane. The electrochemical analysis indicates that the optimized LNMO cathode demonstrates 97.33% capacity retention even after 200 cycles at 1C. Additionally, the material shows a highly satisfactory discharge capacity of 92.3 mAh·g-1at 10C. Overall, microreaction technology is anticipated to offer a novel approach in the synthesis of LNMO cathode materials with excellent performance.

Enhancing the Integral Structural and Thermal Stability of Ultrahigh-Ni Cathodes via Morphology Refinement and In Situ Interfacial Engineering.

Nickel-rich layered oxides are promising cathodes in commercial materials for lithium-ion batteries. However, the increase of the nickel content leads to the decay of cyclic performance and thermal stability. Herein, in situ surface-fluorinated W-doping LiNi0.90Co0.05Mn0.05O2 cathodes enhance integral lithium-ion migration (transfer in bulk and diffusion in the interface) kinetics by synergistically solving the problems of bulk and interface structural degradation. Owing to the introduction of tungsten, the growth of primary particles is regulated toward the (003) crystal plane and with the acicular structure, which further stabilizes the bulk structure during cycling. Moreover, the LiF coating layer on the cathode/electrolyte interface physically isolates the attack of the electrolyte on the surface cathodes and accelerates the lithium-ion diffusion rate, ultimately ameliorating the interfacial dynamics and structural stability. Dual-modified LiNi0.90Co0.05Mn0.05O2 exhibits superior electrochemical properties, especially more remarkable cyclic retention (88.16% vs 70.44%) after 100 cycles at 1 C and more outstanding high current rate properties (173.31 mAh·g-1 vs 135.97 mAh·g-1) at 5 C than the pristine one. This work emphasizes the probability of an integrated optimization strategy for Ni-rich materials, which provides an innovative idea for ameliorating (bulk and interfacial) structure degradation and promoting the diffusion of lithium ions during cycling.