Novel battery technology is surpassing current standards. A significant development in this area is the emergence of solid-state batteries (SSBs). These batteries, which use a solid electrolyte, are an improvement over traditional lithium-ion batteries (LIBs) and offer enhanced safety features.
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Researchers in material science are actively working to advance SSB technology. This article explores some of the latest breakthroughs in this innovative field.
Overview of Solid-State Batteries
SSBs use solid electrolytes, unlike LIBs, which use a liquid electrolyte. An advantage of SSBs is enhanced safety, as solid electrolytes remove the risk of thermal runaway and electrolyte leakage.1 Solid-state batteries also offer higher energy densities, allowing them to store more energy within a smaller footprint.
Portable devices, electric vehicles (EVs), and grid-scale energy storage systems rely on electrochemical power sources like LIBs. However, the commercial LIBs currently in use pose significant safety risks when overcharged since they contain flammable liquid electrolytes.
The energy density of traditional LIBs is also very close to its physiochemical limit. Therefore, the development of technologies with high energy density and intrinsic safety is crucial for large-scale energy-storage systems. As a result, SSBs have seen a resurgence recently for their improved safety and higher energy density.
The transition to SSBs is also promising for addressing challenges in renewable energy storage and EV adoption. By leveraging solid electrolytes, these batteries can withstand extreme temperatures and harsh operating conditions, making them ideal for use in EVs operating in diverse climates.2
Key Innovations in Solid-State Battery Technology
Advancements in SSB technology have focused on enhancing the ionic conductivity and stability of solid electrolytes for safer and more efficient energy storage solutions.
Recently, a group of researchers identified high ionic conductivity in pyrochlore-type oxyfluoride, which remained stable in air.3 This compound exhibited a remarkable bulk ionic conductivity of 7.0 mS cm–1 and a total ionic conductivity of 3.9 mS cm–1 at room temperature (approximately 298 K), surpassing any previously reported oxide solid electrolytes.
The conduction mechanism within this structure involves the sequential movement of Li ions along with changes in bonds with F ions. This discovery not only resulted in the synthesis of a highly conductive and stable solid electrolyte but also introduced a new class of superionic conductors based on pyrochlore-type oxyfluorides.
Considerable efforts have been made to improve polyethylene's low ionic conductivity at ambient temperature. Techniques such as incorporating inorganic fillers to reduce polymer crystallization have been explored.
Since poly(ethylene oxide) (PEO) can coordinate its numerous oxygen atoms with Li-ions, it efficiently facilitates ion conduction within the matrix, making it the most researched polymer in this context. The polymer chains in PEO's amorphous regions are the primary means of ion transport and are crucial for the material's mechanical qualities and conductivity.
The electrochemical properties of PEO have been significantly enhanced by modifying the amount of two distinct liquid crystalline monomers, each with a different length of methylene chain connected to a stiff core and terminal acrylate groups.4 This modification enhances the structural integrity and ion conductivity of the porous polymer network by forming effective ion transport channels.
Due to their solid-state construction, SSBs have less overall weight and volume, eliminating the need for separators and thermal management systems necessary for liquid electrolyte LIBs (LE-LIBs).5 This compactness is particularly beneficial for EVs, helping them save weight and space.
Solid electrolytes in SSBs also have a longer lifespan and a slower rate of capacity reduction over time because they are more stable and degrade less under cycling circumstances. Studies in this area have produced materials whose ionic conductivities are either as high as or higher than those of their liquid equivalents.6
Compared to liquid electrolytes, which tend to degrade over time and under heat stress, solid electrolytes found in supercapacitors are less susceptible to degradation. Researchers have found that the inherent stability of solid electrolytes helps SSBs last longer, which lowers the need for frequent battery replacements and, over time, lessens the environmental and economic impacts of battery disposal.7
Since SSBs have no liquid components, more design flexibility is available. This enables the production of batteries in sizes and configurations that were previously impossible, creating new opportunities for integrating batteries into various products and applications, from wearable electronics to renewable energy sources.8
Challenges to Commercialization
Despite the many benefits SSBs provide, several challenges must be addressed before they can be produced on a large scale.
Firstly, the production of SSBs involves complex manufacturing processes that are currently difficult to scale. It requires precise engineering and management to fabricate tiny, flawless layers of solid electrolyte and ensure ideal contact with the electrodes. A major challenge for making SSBs commercially viable is scaling these techniques to mass production while maintaining quality and consistency.
Additionally, the thermal management of SSBs remains a challenge despite their inherent safety and stability at high temperatures, particularly in high-power applications such as electric vehicles. Compared to liquid electrolytes, solid electrolytes have a less effective heat-dissipation capacity. For SSBs to function correctly and have a long lifespan, heat management during fast charge and discharge cycles must be carefully considered in the design.
Lastly, many solid electrolytes, especially those made of ceramic, are brittle, making them difficult to handle and more prone to failure. It is imperative to develop solid electrolytes with sufficient mechanical strength to endure these shocks.
Future Outlook for Solid-State Batteries
As research endeavors persist in pushing the boundaries of ingenuity, addressing pivotal challenges such as manufacturing scalability, thermal regulation, and mechanical resilience, SSBs are set to significantly impact the transition toward cleaner and more sustainable energy systems.
With continual strides in materials science, battery architecture, and production methodologies, SSBs are anticipated to increasingly rival conventional LIBs, offering enhanced safety profiles, augmented energy densities, and protracted operational lifespans.
As collaborative efforts within the sector increase, the widespread commercialization of SSBs holds the potential to drive significant advances toward a more eco-friendly and efficacious energy landscape.
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References and Further Readings
[1] Wang, C., et al. (2023). The Promise of Solid-State Batteries for Safe and Reliable Energy Storage. Engineering. doi.org/10.1016/j.eng.2022.10.008.
[2] Machín, A., et al. (2024). Advancements and Challenges in Solid-State Battery Technology: An In-Depth Review of Solid Electrolytes and Anode Innovations. Batteries. doi.org/10.3390/batteries10010029.
[3] Aimi, A., et al. (2024). High Li-ion conductivity in pyrochlore-type solid electrolyte Li2-xLa(1+x)/3M2O6F. Chemistry of Materials. doi.org/10.1021/acs.chemmater.3c03288
[4] Wang, M., et al. (2023). Accelerated ion transportation in liquid crystalline polymer networks for superior solid-state lithium metal batteries. Chem. Eng. doi.org/10.1016/j.cej.2023.146658.
[5] Janek, J., et al. (2023). Challenges in speeding up solid-state battery development. Nat. Energy. doi.org/10.1038/s41560-023-01208-9.
[6] Xu, L., et al. (2022). Recent advances of composite electrolytes for solid-state Li batteries. J. Energy Chem. doi.org/ 10.1016/j.jechem.2021.10.038.
[7] Waidha, A., et al. (2023). Recycling of All-Solid-State Li-ion Batteries: A Case Study of the Separation of Individual Components Within a System Composed of LTO, LLZTO and NMC. ChemSusChem. doi.org/10.1002/cssc.202202361
[8] Pandey, G., et al. (2022). Architectural Design for Flexible Solid-State Batteries. Solid State Batteries. doi.org/ 10.1021/bk-2022-1414.ch013.
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