A Fully Amorphous, Dynamic Cross-Linked Polymer Electrolyte for Lithium-Sulfur Batteries Operating at Subzero-Temperatures.

Solid-state lithium-sulfur batteries have shown prospects as safe, high-energy electrochemical storage technology for powering regional electrified transportation. Owing to limited ion mobility in crystalline polymer electrolytes, the battery is incapable of operating at subzero temperature. Addition of liquid plasticizer into the polymer electrolyte improves the Li-ion conductivity yet sacrifices the mechanical strength and interfacial stability with both electrodes. In this work, we showed that by introducing a spherical hyperbranched solid polymer plasticizer into a Li+ -conductive linear polymer matrix, an integrated dynamic cross-linked polymer network was built to maintain fully amorphous in a wide temperature range down to subzero. A quasi-solid polymer electrolyte with a solid mass content >90 % was prepared from the cross-linked polymer network, and demonstrated fast Li+ conduction at a low temperature, high mechanical strength, and stable interfacial chemistry. As a result, solid-state lithium-sulfur batteries employing the new electrolyte delivered high reversible capacity and long cycle life at 25 °C, 0 °C and -10 °C to serve energy storage at complex environmental conditions.

Micrometer-Sized SiMgy Ox with Stable Internal Structure Evolution for High-Performance Li-Ion Battery Anodes.

In recent years, micrometer-sized Si-based anode materials have attracted intensive attention in the pursuit of energy-storage systems with high energy and low cost. However, the significant volume variation during repeated electrochemical (de)alloying processes will seriously damage the bulk structure of SiOx microparticles, resulting in rapid performance fade. This work proposes to address the challenge by preparing in situ magnesium-doped SiOx (SiMgy Ox ) microparticles with stable structural evolution against Li uptake/release. The homogeneous distribution of magnesium silicate in SiMgy Ox contributes to building a bonding network inside the particle so that it raises the modulus of lithiated state and restrains the internal cracks due to electrochemical agglomeration of nano-Si. The prepared micrometer-sized SiMgy Ox anode shows high reversible capacities, stable cycling performance, and low electrode expansion at high areal mass loading. A 21700 cylindrical-type cell based on the SiMgy Ox -graphite anode and LiNi0.8 Co0.15 Al0.05 O2 cathode demonstrates a 1000-cycle operation life using industry-recognized electrochemical test procedures, which meets the practical storage requirements for consumer electronics and electric vehicles. This work provides insights on the reasonable structural design of micrometer-sized alloying anode materials toward realization of high-performance Li-ion batteries.

Enabling SiOx/C Anode with High Initial Coulombic Efficiency through a Chemical Pre-Lithiation Strategy for High-Energy-Density Lithium-Ion Batteries.

Carbon-coated SiOx microparticles (SiOx/C) demonstrate attractive potential for anode use in high-energy-density lithium-ion batteries due to high capacity and proper cycling stability. However, the excessive irreversible consumption of Li ions during the initial cycling remains a serious challenge arising from the limited lithium in full cells. Here, we endow SiOx/C anode with high initial Coulombic efficiency using the chemical pre-lithiation strategy. The lithium silicate is uniformly pregenerated in SiOx/C microparticles, which could effectively counteract the irreversible consumption of Li ions and avoid the complicated pre-lithiation process. Moreover, this strategy guarantees the structural integrity and processability of anode materials because of the homogeneous Li-organic complex solution pre-lithiation and high-temperature calcination process. The obtained SiOx/C microparticles can be applied as anode materials by directly mixing with commercial graphite, which demonstrates proper specific capacity, high initial Coulombic efficiency, and excellent cycling performance. Furthermore, the pouch cells using LiNi0.8Co0.1Mn0.1O2 cathodes and the as-prepared anodes exhibit high energy density (301 Wh kg-1) and satisfactory cycling stability (93.3% capacity retention after 100 cycles).