Samsung recently announced the development of a groundbreaking solid-state electric vehicle (EV) battery (Figure 1), promising a 600-mile range, 9-minute rapid charging, and a 20-year lifespan. In contrast, EVs with conventional lithium-ion (Li-ion) batteries typically offer a 250- to 350-mile range, 25- to 30-minute rapid charging, and an 8- to 15-year lifespan. Although many major automotive manufacturers have expressed interest in replacing conventional Li-ion batteries with solid-state alternatives, mass adoption has yet to be achieved.

This article reviews the primary limitations of conventional EV Li-ion batteries and highlights the key potential advantages of their solid-state counterparts. It also discusses the various challenges in developing and integrating solid-state EV batteries, ranging from solid electrolyte stability and brittleness to thermal management and lithium dendrite formation. Lastly, the article explores some technical advances driving solid-state battery commercialization.

Limitations of conventional Li-ion batteries

Containing liquid electrolytes, conventional Li-ion batteries power nearly all EVs on the road today. Delivering massive amounts of electric current to zero-emission motors, these batteries offer EV owners a greener alternative to internal combustion engine (ICE) vehicles. Some industry watchers, however, continue to voice concerns over various limitations, such as battery performance degradation, safety, and environmental impact.

For example, continuous charging and discharging cycles lead to an inevitable and gradual decline in battery capacity (energy storage), a process accelerated by frequent rapid charging. Liquid electrolytes also introduce risks such as leakage and dendrite formation, characterized by needle-like structures forming within the battery. Notably, dendritic growth remains a critical failure mechanism for conventional Li-ion batteries, increasing the risk of short circuits, thermal runaway, and even explosions.

Additionally, electrolyte leakage caused by mechanical stress or thermal expansion can trigger harmful chemical reactions outside the battery compartment, potentially damaging adjacent electronic circuits or cooling systems. Maintaining temperature-dependent ionic conductivity further impacts battery efficiency and longevity, as extreme fluctuations in external temperature, whether heat or cold, can degrade performance. Lastly, the extraction and shipment of key elements like lithium and cobalt from mines scattered around the globe raise environmental concerns, as do end-of-life disposal and recycling.

Advantages of solid-state batteries

Many solid-state battery designs (Figure 2) promise significant advantages over conventional lithium-ion batteries. By using non-flammable solid electrolytes, these batteries eliminate the risk of liquid electrolyte leakage and significantly reduce the potential for fires and explosions. Despite design challenges, solid-state batteries aim to maintain consistent performance across a wide range of temperatures.

Solid-state batteries can significantly extend EV driving range by achieving higher energy density by incorporating lithium-metal anodes and compact designs that maximize energy storage per unit volume. In addition to conducting ions, solid electrolytes function as a separator, preventing short circuits by keeping the anode and cathode apart. This increased energy density, combined with advances in solid electrolyte materials, facilitates faster and safer charging, as solid electrolytes can better withstand high currents, effectively reducing the risk of overheating.

Because solid electrolytes are more stable and resistant to degradation, solid-state battery designs offer a longer lifespan and more reliable energy storage (capacity). Lastly, these batteries reduce the use of toxic materials by eliminating volatile organic compounds found in liquid electrolytes and minimizing reliance on certain heavy metals.

Challenges of solid-state batteries

Many automotive manufacturers prioritize the development of solid-state batteries to achieve higher energy storage capacity, faster charging times, and improved safety.

However, mass adoption is still limited by various design and manufacturing challenges (Figure 3), including:

• Solid electrolyte behavior: Engineering teams may lack a consistent and comprehensive analysis of solid electrolyte behavior. The absence of real-world feedback from EV solid-state battery management systems (BMS) and thermal management systems (TMS), particularly regarding temperature fluctuations and mechanical stress, limits performance optimization.
• Stability: Achieving consistently stable interfaces between the solid electrolyte and electrodes is still a work in progress for many design teams. Solid electrolytes can create poor contact and high interfacial resistance (the resistance encountered at the boundary between the electrolyte and the electrode during ion transport), especially during charging and discharging, potentially leading to performance degradation.
• Brittleness: The brittleness of many solid electrolytes, particularly ceramics, complicates handling during manufacturing and reduces durability on roads and highways. Vibrations and stress can cause battery cracks and mechanical failure if not addressed effectively.
• Lithium dendrite formation: Although solid-state designs significantly reduce the risk of dendrite formation compared to conventional Li-ion batteries, the issue persists with lithium-metal anodes. Needle-like structures can still form during charging, leading to dendrite growth, short circuits, and battery failure.
• Thermal management: Solid electrolytes can better withstand high currents but are less efficient at dissipating heat than liquid electrolytes. Additionally, their lower thermal conductivity complicates heat management, especially under high-power conditions and extreme cold temperatures, where maintaining optimal ionic conductivity becomes challenging.
• Complexity and scalability: Producing solid-state batteries involves complex, difficult-to-scale fabrication processes and costly solid electrolyte materials that provide high ionic conductivity, mechanical strength, and stability. Creating defect-free, thin solid electrolyte layers and ensuring precise contact with electrodes require advanced engineering facilities. At the same time, dry rooms are often necessary to prevent moisture from degrading sensitive materials such as sulfide-based solid electrolytes.

Technical advances and innovations

Automotive companies and research institutions use advanced materials and innovative engineering techniques to accelerate solid-state battery development. For example, sulfide-based and oxide-based materials reinforce the durability of solid electrolytes by providing high ionic conductivity and improved thermal stability.

Composite electrolytes, which combine inorganic and organic components, bolster mechanical stability and maintain optimal thermal levels, effectively reducing the risk of electrolyte degradation and failure. Additionally, integrating nanomaterials into these electrolytes enhances their structural integrity. In contrast, hybrid solid electrolytes, combining the best properties of inorganic and polymer materials, improve mechanical flexibility and electrochemical performance.

Protective coatings and interlayers act as barriers between the electrolyte and electrodes, mitigating interface instability, while additives such as borosilicate glass (BG) in the solid electrolyte matrix improve structural integrity and thermal shock resistance. This minimizes the risks of cracking and delamination, particularly under mechanical stress or rapid temperature changes. Moreover, advanced thermal management systems effectively dissipate heat and help prevent catastrophic failures caused by exothermic (heat-releasing) reactions.

Manufacturing techniques like cold sintering and thin-film deposition facilitate the scalable production of defect-free, ultrathin solid electrolytes with uniform interfaces. This ensures improved contact between the solid electrolyte and electrodes, reducing interfacial resistance and bolstering battery safety and performance. High-capacity cathode materials, such as nickel-rich layered oxides and lithium-rich compounds, complement the high-energy-density potential of solid-state batteries.

Lastly, advanced simulation tools (Figure 4) are crucial in optimizing solid-state battery designs by modeling ion transport and predicting material behavior under various conditions. These simulation tools enable researchers to refine battery architectures and boost performance before physical prototyping and production.

Summary

Current EVs with conventional Li-ion batteries typically offer a 250 to 350-mile range, 25 to 30-minute rapid charging, and an 8 to 15-year lifespan. In contrast, new solid-state EV battery designs from companies like Samsung promise a 600-mile range, 9-minute rapid charging, and a 20-year lifespan. While many automotive manufacturers aim to replace conventional Li-ion batteries with solid-state alternatives, significant barriers to mass adoption remain, ranging from solid electrolyte brittleness and lithium dendrite formation to complexity and scalability. Automotive engineers successfully address these challenges with advanced materials, techniques, and simulations.

References

Advancements and Challenges in Solid-State Battery Technology: An In-Depth Review of Solid Electrolytes and Anode Innovations, MDPI
Challenges and Advancements in All-Solid-State Battery Technology for Electric Vehicles, MDPI
Solid-State Batteries: Potential and Challenges On the Way to the Mass Market, Fraunhofer
Solid-State Battery Tech For EVs: 600 Miles of Range in 9 Minutes? MotorTrend
Solid-State Batteries Could Face “Production Hell,” IEEE Spectrum
Review on Current State, Challenges, and Potential Solutions in Solid-State Batteries Research, ScienceDirect
Navigating the Future: A Guide to Solid-State Batteries for Electric Cars, Midtronics