As low-altitude economies take flight, the race to power electric vertical take-off and landing (eVTOL) vehicles has intensified. At the heart of this revolution lies a critical enabler: solid-state battery. These advanced energy storage systems promise to address the unique demands of aerial mobility, balancing energy density, power output, and safety—a triad historically deemed incompatible.
The eVTOL Challenge: An “Impossible Trinity”
Low-altitude aviation introduces unprecedented requirements for battery technology. Unlike ground-based electric vehicles, eVTOLs demand rapid vertical ascent, sustained hovering, and efficient cruising—all within minutes. This necessitates:
- High Energy Density: To maximize payload and range.
- Ultra-High Power Density: To deliver 3C–8C discharge rates, 6–10× higher than conventional EV batteries.
- Uncompromising Safety: To prevent thermal runaway during high-stress operations.
Traditional lithium-ion batteries struggle to reconcile these competing priorities. For instance, during descent, eVTOL batteries often operate at 20–30% state-of-charge (SOC) while sustaining peak power output—a scenario absent in terrestrial EVs. The result is an energy-power-safety trilemma that conventional chemistries cannot resolve.
Solid-State Battery: Breaking the Trilemma
Solid-state battery (SSBs) replace liquid electrolytes with solid conductive materials, unlocking transformative advantages:
| Parameter | Li-ion Battery | Semi-Solid Battery | Solid-State Battery |
|---|---|---|---|
| Energy Density (Wh/kg) | 250–300 | 320–360 | 400–500 (projected) |
| Discharge Rate (C-rate) | 0.1–0.5 | 1–3 | 3–8 |
| Thermal Stability | Moderate | Improved | Exceptional |
| Cycle Life | 1,000–2,000 | 1,500–3,000 | 5,000+ (target) |
SSBs achieve these metrics through:
- Dense Electrode Architectures: Enabling higher energy storage per unit mass.
- Non-Flammable Electrolytes: Eliminating fire risks during thermal stress.
- Faster Ion Transport: Reducing internal resistance for high-power bursts.
The energy density (EdEd) of a battery can be modeled as:Ed=Cell Capacity (Ah)×Average Voltage (V)Mass (kg)Ed=Mass (kg)Cell Capacity (Ah)×Average Voltage (V)
For SSBs, EdEd is projected to exceed 500 Wh/kg by 2030, aligning with China’s General Aviation Equipment Innovation Application Plan (2024–2030), which mandates 400 Wh/kg batteries for mass production and 500 Wh/kg prototypes for validation.
Bridging the Gap: Hybrid Solutions and Customization
While SSBs represent the ultimate goal, interim solutions are critical for accelerating eVTOL commercialization. Companies like SVOLT and Farasis Energy are adopting hybrid strategies:
- Semi-Solid Batteries: Combining partial solid electrolytes with liquid components to boost safety and energy density.
- Modular Packs: Tailoring battery configurations to mission profiles (e.g., short-haul vs. long-range).
For example, SVOLT’s Gen1 and Gen2 aviation batteries deliver 320 Wh/kg and 360 Wh/kg, respectively, using semi-solid technology. Such innovations allow manufacturers to prioritize parameters based on operational needs:
- High-Frequency, Short-Distance Flights: Sacrifice charge speed for reliability via swappable battery systems.
- Long-Endurance Missions: Integrate hybrid electric-combustion powertrains.
Safety: The Non-Negotiable Imperative
“Three feet above ground, lives are at stake,” emphasizes Professor Yan Feng of the Civil Aviation Flight University of China. SSBs inherently address safety concerns through:
- Intrinsic Stability: Solid electrolytes resist dendrite formation, a primary cause of short circuits.
- Aging Resilience: SVOLT’s stress tests simulate 1,000+ charge-discharge cycles under flight conditions, ensuring performance degradation remains below 20%.
The safety factor (SfSf) of a battery under thermal stress is defined as:Sf=Thermal Runaway Onset Temperature (°C)Maximum Operating Temperature (°C)Sf=Maximum Operating Temperature (°C)Thermal Runaway Onset Temperature (°C)
SSBs exhibit Sf>2.5Sf>2.5, compared to Sf<1.5Sf<1.5 for liquid-based systems.
The Road Ahead: Collaboration and Innovation
The low-altitude economy demands cross-industry synergy. Battery manufacturers must collaborate with eVTOL developers to:
- Standardize Testing Protocols: Create aviation-specific benchmarks for energy, power, and safety.
- Optimize Supply Chains: Secure raw materials (e.g., lithium, sulfides) for scalable SSB production.
- Leverage Data Analytics: Use flight telemetry to refine battery management systems (BMS).
As Xu Zhongling, Head of SVOLT’s Central Research Institute, states, “Customization is non-negotiable. We’re partnering with OEMs to co-develop batteries that meet the granular needs of low-altitude flight.”
Conclusion: Solid-State Battery as the Linchpin
The ascent of eVTOLs hinges on solid-state battery. While current hybrids and semi-solid systems bridge near-term gaps, SSBs will ultimately dominate due to their unparalleled performance and safety. For stakeholders, the imperative is clear: Invest in SSB R&D today to secure a leadership position in tomorrow’s aerial mobility ecosystem.
By 2030, SSBs will not only power eVTOLs but also redefine energy storage across aerospace, maritime, and automotive sectors. The sky is no longer the limit—it’s the beginning.