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The ambient temperature application of PEO-based polymer electrolytes has been restrained by their poor ionic conductivity. Herein, we report a super-concentrated polymer in “solvated ionic liquid” which is composed of polyethylene oxide (PEO), LiN(SO2CF3)2 (LiTFSI), and solvent with low viscosity. It is found that the maximum coordination during Li, polymer, and the solvent can be formed by the molar ratio of PEO/Li = 1:1 with 25 wt% of solvent, left no free solvent exits in the mixture. The electrochemical performance of the designed electrolyte was evaluated by using a LiFePO4/Li cell. Comparing to the conventional carbonate liquid electrolyte, the designed electrolyte achieves comparable rate performance (155.4 and 157.8 mAh g−1 discharge at 1 C for the designed and carbonate electrolyte, respectively) and higher cycle performance (capacity retention of 95.5% and 75.5% after 100 cycles for the designed and carbonate electrolyte, respectively). It has been further proven that incombustibility can be obtained by only adding ~15 wt% fire-retardant. We believe that the developed electrolyte is promising and practical for being applied in the polymer lithium-ion battery.

The requirements for volume and weight performance are becoming more and more urgent for the application of lithium-ion batteries in consumer electronics and electric vehicles. Herein, we demonstrate a facial and cost-effective synthesis approach of lithium-ion conducting glass ceramic (LICGC)/reduced graphene oxide (rGO) composite, in which the LICGC particles anchor on the rGO sheets densely and homogenously, forming a sandwich-like structure. The unique feature offers ultrafast Li-ion and electron pathways through the LICGC network and rGO sheets, resulting in the enhancement of the rate and cycle performances for the electrodes. For example, the results show that for LiFePO4 cathode with the polymer electrolyte, the addition of 10 wt% of LICGC/rGO composite achieved the higher rate capability (~122 mAh g−1, discharge at 3 C) and cyclability (~98.2% after 180 cycles at 1 C), compared to add LICGC only (~115 mAh g−1 and ~93.4%, respectively).

A high-capacity thick cathode has been studied as one of ways to improve the energy density of lithium secondary batteries. In this study, the LiFePO 4 cathode with a capacity per unit area of 8.4 m Ah cm −2 corresponding to four times the capacity of conventional cathodes has been developed using a three-dimensional porous aluminum current collector called “FUSPOROUS”. This unique current collector enables the smooth transfer of electrons and Li + -ions through the thick cathode, resulting in a good rate capability (discharge capacity ratio of 1.0 C/0.2 C = 0.980) and a high charge-discharge cycle performance (80% of the initial capacity at 2000th cycle) even though the electrode thickness is 400 μm. To take practical advantage of the developed thick cathode, conceptual designs for a 10-Ah class cell were also carried out using graphite and lithium-metal anodes.

Li metal battery with garnet-type Li7La3Zr2O12 (LLZ) as a solid electrolyte has attracted attentions as a promising candidate for high-energy batteries. However, the interfacial resistance between LLZ and Li is huge due to a point-point contact, leading to poor battery performances such as rate capability and cycleability. Here, we have studied the hybrid-electrolyte structure using the liquid electrolyte interlayer containing LiBH4 between LLZ and Li at high operating temperature of 120 °C. This hybrid-electrolyte structure offers high current density usage and a long-term cycleability. The Li|LLZ|Li symmetric cell shows high critical current density of 13 mA cm−2 and a long term cycle. The liquid electrolyte interlayer containing LiBH4 provides an improved coulombic efficiency of Li striping/plating due to an excellent reductive stability. Our findings suggest that the interfacial conditions on LLZ|Li could be effectively improved by using the modified liquid electrolyte interlayer.

Graphene has attracted considerable attention as the conductive agent for lithium batteries by providing a superior interfacial contact. However, the wrapping of active materials by the large area of graphene sheets may hinder the transportation of Li+ between active particles and electrolyte, especially at a high charge/discharge rates. Herein, holey graphene oxide (h-GO), which is made by a green wet ball-milling of GO in one step without using any catalysts or chemicals, is combined with carbon nanotubes (CNTs) and LiMn0.7Fe0.3PO4 (LMFP) to make a composite cathode for lithium batteries. Results show that after the electrochemical reduction, the LMFP cathode with h-GO/CNT shows remarkedly improved electrochemical performances due to the facilitated Li+ transport pathway, compared to that with conventional GO/CNT. For example, LMFP/h-GO/CNT composite cathode can achieve a discharge capacity of 112 mAh g−1 when discharged at 20 C, while LMFP electrode with conventional GO/CNT only shows a discharge capacity of 35 mAh g−1. This study provides a new approach for fabricating holey graphene and can open up new possibilities for applications on power sources.