Abstract
To inhibit Li-dendrite growth on lithium (Li)-metal electrodes, which causes capacity deterioration and safety issues in Li-ion batteries, we prepared a porous polyimide (PI) sponge using a solution-processable high internal-phase emulsion technique with a water-soluble PI precursor solution; the process is not only simple but also environmentally friendly. The prepared PI sponge was processed into porous PI separators and used for Li-metal electrodes. The physical properties (e.g., thermal stability, liquid electrolyte uptake, and ionic conductivity) of the porous PI separators and their effect on the Li-metal anodes (e.g., self-discharge and open-circuit voltage properties after storage, cycle performance, rate capability, and morphological changes) were investigated. Owing to the thermally stable properties of the PI polymer, the porous PI separators demonstrated no dimensional changes up to 180 °C. In comparison with commercialized polyethylene (PE) separators, the porous PI separators exhibited improved wetting ability for liquid electrolytes; thus, the latter improved not only the physical properties (e.g., improved the electrolyte uptake and ionic conductivity) but also the electrochemical properties of Li-metal electrodes (e.g., maintained stable self-discharge capacity and open-circuit voltage features after storage and improved the cycle performance and rate capability) in comparison with PE separators.
Highlights
Portable electronic devices such as cellphones and laptops have revolutionized modern society
Li-ion batteries (LIBs) are on the verge of transforming the transportation and energy-storage sectors by enabling the development of efficient electric vehicles (EVs) and energy storage systems (ESSs)
The ionic salt phase of poly(amic acid) (PAA) stabilized the oil and water interface without phase inversion at a high volume–fraction of dispersed oil droplets and allowed micrometer-sized oil droplets to be well-dispersed in the continuous phase (Figure 1c)
Summary
Portable electronic devices such as cellphones and laptops have revolutionized modern society. Li-ion batteries (LIBs), which power mobile electronic devices, have been crucial for this revolution [1,2,3]. LIBs are on the verge of transforming the transportation and energy-storage sectors by enabling the development of efficient electric vehicles (EVs) and energy storage systems (ESSs). Large-scale electrical applications such as EVs and ESSs require high-energy-density batteries, whose performances surpass those of traditional LIBs. the development of new electrode systems has attracted immense attention. Because the energy density of batteries is determined by the product of capacity and operating voltage (i.e., energy = voltage × capacity), Li metal, which has the highest theoretical capacity (3860 mAh g−1) and the lowest operating potential (−3.04 V versus standard hydrogen electrode) among the candidates for anode active material, has been considered as a promising anode active material [4]
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