Abstract
Sodium superionic conductor (NASICON)-type lithium aluminum germanium phosphate (LAGP) has attracted increasing attention as a solid electrolyte for all-solid-state lithium-ion batteries (ASSLIBs), due to the good ionic conductivity and highly stable interface with Li metal. However, it still remains challenging to achieve high density and good ionic conductivity in LAGP pellets by using conventional sintering methods, because they required high temperatures (>800 °C) and long sintering time (>6 h), which could cause the loss of lithium, the formation of impurity phases, and thus the reduction of ionic conductivity. Herein, we report the utilization of a spark plasma sintering (SPS) method to synthesize LAGP pellets with a density of 3.477 g cm−3, a relative high density up to 97.6%, and a good ionic conductivity of 3.29 × 10−4 S cm−1. In contrast to the dry-pressing process followed with high-temperature annealing, the optimized SPS process only required a low operating temperature of 650 °C and short sintering time of 10 min. Despite the least energy and short time consumption, the SPS approach could still achieve LAGP pellets with high density, little voids and cracks, intimate grain–grain boundary, and high ionic conductivity. These advantages suggest the great potential of SPS as a fabrication technique for preparing solid electrolytes and composite electrodes used in ASSLIBs.
Highlights
The utilization of rechargeable lithium-ion batteries (LIBs) has been increasingly expanded from consumer devices to plug-in or hybrid electric vehicles and smart grid energy storage systems, in order to alleviate the dependence on fossil fuels, decrease greenhouse gas emissions, and realize clean transportation [1,2]
Highly densified lithium aluminum germanium phosphate (LAGP) pellets were fabricated by using spark plasma sintering (SPS) technique and exhibited high ionic conductivity at room temperature
The influence of SPS sintering temperatures (600–750 ◦C) and times (1–10 min) on the microstructure, density, and ionic conductivity of the LAGP pellets were studied in detail
Summary
The utilization of rechargeable lithium-ion batteries (LIBs) has been increasingly expanded from consumer devices to plug-in or hybrid electric vehicles and smart grid energy storage systems, in order to alleviate the dependence on fossil fuels, decrease greenhouse gas emissions, and realize clean transportation [1,2]. The adoption of SSEs can significantly reduce the safety risks associated with the flammable, volatile, and toxic liquid organic electrolytes, and could potentially address the Li dendrite growth problem and make it possible for the utilization of Li metal with a high theoretical capacity of 3860 mA h g−1 as the anode, substantially elevating energy densities and the safety of ASSLIBs. Among different kinds of SSEs, including garnet [9,10], perovskite [11,12], sulfides [13], hydrides [14], borate or phosphate [15,16,17], halides [18], lithium phosphorousoxynitride (LiPON) [19], lithium superionic conductor (LISICON) [20,21,22,23], and other Li-based ceramic [24], sodium superionic conductor (NASICON)-type is one of the most popular solid electrolytes, due to its high ionic conductivity and good chemical and thermal stability with lithium anode [25,26,27,28]. The low operating SPS temperature avoided the formation of ionic nonconductive impurities, which usually appeared in the grain boundaries for traditionally high-temperature sintered samples and resulted in blocking of Li-ion transport pathways
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