Hybrid solid-liquid batteries are a blend of traditional ones with liquid electrolytes, and solid-state ones with solid electrolytes. Whichever the case may be, electrolytes are a critical feature of all batteries. This is because they are highways along which charged ions travel between electrodes.
Liquid Electrolyte Batteries Are Center Stage
Liquid electrolytes continue to command the battery market. They conduct ions easily, and accept and release energy readily. However, as numerous incidents involving lithium-ion batteries demonstrate, liquid electrolytes can leak, evaporate, or in rare cases catch fire.
Solid-State Chemistry Faces Challenges
A solid-state battery replaces the entire liquid electrolyte with a solid material, such as a ceramic, polymer, or glass. This arrangement can improve safety because such solids are usually non-flammable and less prone to leakage.
Interestingly, the solid material may also permit the use of high-energy materials, such as lithium metal anodes. However, fully-solid systems still face engineering challenges, including maintaining good contact between electrodes and electrolytes, without which battery performance suffers.
Hybrid Solid-Liquid Batteries Beckon
Hybrid solid–liquid batteries combine the advantages of both approaches. In these instances the main electrolyte structure is solid. But a small amount of liquid or gel is included at the interfaces between the electrodes and the solid electrolyte.
This liquid layer may improve ion transport, and help maintain stable contact between materials during charge and discharge cycles. This approach improves ionic conductivity, and reduces internal resistance. The solid framework also limits leakage and improves structural stability as well.
Such hybrid electrolytes could enable a transition between conventional liquid-electrolyte batteries, and future fully-solid-state designs. They may provide many of the safety and stability benefits of solid electrolytes, while retaining some of the advantages of liquid-based ones.
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