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Battery technology is evolving rapidly, and two major contenders are solid-state and lithium-ion batteries. While lithium-ion batteries power everything from smartphones to EVs, solid-state models promise better energy density, faster charging, and improved safety. But are solid-state batteries worth the wait, or will lithium-ion remain the dominant choice in the near future? This article breaks down the key differences, advantages, and challenges of both technologies to help you understand which battery type is best for different applications.
What Is a Solid State Battery?
A solid-state battery is a rechargeable battery that contains no liquid electrolytes. Instead, it uses a solid electrolyte to move ions between the electrodes during charging and discharging.
How Do Solid State Batteries Work?
Solid-state batteries have an anode of lithium or lithium alloy and a cathode of metal oxides (nickel, manganese, cobalt), similar to traditional lithium-ion models. However, in this case, the electrolyte is solid and made of ceramics, polymers, or sulfides. The separator is part of the solid medium and no longer needs to physically separate the anode and cathode in a liquid medium. This saves significant weight and space compared to those made with liquids.
When charging, the lithium ions flow through the solid electrolyte and form a solid layer of lithium on the anode. This has a smaller volume than the anode in a lithium-ion battery with liquid electrolytes, allowing more energy to be generated by a smaller battery.
Applications
Solid-state models are not yet commercially available as they’re still in the research and development phases. However, they’re expected to reach the EV market as early as 2026 or 2027 and will likely start entering additional markets around the same time. They could be used in the renewable energy sector, electronic devices, industrial applications, drones, pacemakers, and more.
Advantages
One significant advantage is their much higher energy density potential. This means you can produce batteries that can achieve the same mAh capacity as traditional lithium-ion models but are more compact and weigh significantly less. They also have the potential for improved longevity and ultra-fast charging capabilities because they are less affected by temperature extremes.
Another advantage is that their non-flammable solid electrolyte significantly reduces safety issues with fire risk or gas venting, which is also less susceptible to temperature extremes.
Disadvantages
The main disadvantages are that solid electrolytes are more expensive than liquid ones, the manufacturing process is more complex, and the existing manufacturing equipment cannot be used. All of this means they are currently much more expensive.
Current technical challenges to overcome include crack formation in the solid electrolyte during charging, which can increase resistance and reduce performance over time. Another issue is that achieving conductivity of the ions comparable to liquid electrolytes remains challenging.
Still, researchers are working to overcome these challenges and get production to a commercial scale. While we may start seeing them come out in the next couple of years, it could still take 5-10 years before they’re widely commercially available. In the meantime, we have products like the EcoFlow DELTA 3, a powerful solar generator with the safest and most durable LiFePO4 chemistry available today.
What Is a Lithium-Ion Battery?
A lithium-ion or Li-ion battery is another rechargeable model that uses lithium ions that travel through a liquid electrolyte to store and release energy.
How Do Lithium-Ion Batteries Work?
These have an anode usually made of graphite and a cathode made of nickel, manganese, cobalt, or iron phosphate with a liquid electrolyte made of salt dissolved in an organic solvent. A separator is placed in the liquid electrolyte between the anode and cathode. Lithium ions move through the liquid electrolyte past the separator during charging and discharging, flowing in one direction to charge and in the opposite direction to discharge when used to power our devices.
Applications
These batteries are widely used today in electric vehicles (EVs), renewable energy storage systems, and almost all modern electronic devices, including tablets, laptops, smartphones, and more.
Advantages
Li-ion models are widely available in various battery capacities, making them very affordable to purchase and use. They also offer moderate to fast charging.
Most Li-ion models are rechargeable, unlike alkaline batteries. Still, there are many different types of lithium batteries, and not all are created equal.
Our newer lithium-iron-phosphate, also called LiFePO4 or LFP, models are safer than ever since they’re much less prone to thermal runaway than their predecessors were. Ongoing research has made the LiFePO4 the superior commercially available option in terms of performance, charging cycles, lifespan, and safety.
For instance, the EcoFlow Portable Power Stations all use LiFePO4 chemistry, making them a superior choice. They come in a wide range of capacities to suit any application you may need. For instance, the compact and lightweight EcoFlow RIVER 3 Series Portable Power Stations can fit in a backpack, while the powerhouse EcoFlow DELTA Series Portable Power Stations come in a range of sizes from a mini generator for your RV to a whole home generator solution that supplies large off-grid homes with electricity.
Disadvantages
While social media often overstates the actual risk, the liquid electrolytes in lithium-ion batteries can pose a flammability risk if they are excessively overheated.
Another disadvantage is that, while far superior to both alkaline and lead acid batteries in terms of longevity, the chemical reactions within them will degrade over time, especially when exposed to temperature extremes.
Solid State Battery vs. Lithium-Ion: Key Differences
Energy Density
The energy density of Li-ion models currently used in EVs ranges from 160 Wh/kg to 250 Wh/kg. On the other hand, solid-state models currently show density potentials of 250-800 Wh/kg, depending on the type. One being researched by Mercedes claims to have achieved 450 Wh/kg in a solid-state battery that is 33% smaller and 40% lighter than comparable Li-ion models.
Safety
While the safety of Li-ion, especially LiFePO4, has dramatically improved over the years, there is still a small risk of the liquid electrolytes overheating and posing a fire risk.
Solid-state batteries have a non-flammable solid electrolyte, significantly reducing the risk of fire and eliminating the rare risk of gas venting. They’re also less susceptible to temperature extremes that make safety issues riskier with liquid electrolytes.
Charging Speed
Lithium-ion models offer moderate to fast charging capabilities but are more sensitive to extreme heat and cold, affecting their charging and discharging cycles.
Solid-state batteries are still in the research phases, but they show good promise for ultra-fast charging capabilities, and their charging speeds are less affected by temperature fluctuations.
Lifespan and Durability
Li-ion batteries were game changers when they first came on the scene in terms of lifespan and durability. LiFePO4 improved on that even further. Still, lithium-ion batteries will degrade over time due to chemical reactions within them. Again, solid-state forms are still being researched and developed, but they promise a longer lifespan once we overcome technical challenges like crack formation in the solid electrolyte during charging and discharging.
Frequently Asked Questions
Lithium-ion batteries are available now, while solid-state models are still in research and development, and their production is currently costly. However, solid-state models show great potential for improved energy density, safety, and charging speed once we overcome technical challenges and bring manufacturing up to commercial scale.
Final Thoughts
Both solid-state and lithium-ion batteries have their strengths. Lithium-ion is widely available, affordable, and proven, making it the current go-to for electronics, EVs, and solar applications. Meanwhile, solid-state batteries promise higher energy density, enhanced safety, and longer lifespan—but they aren’t commercially viable yet. As advancements continue, solid-state technology may revolutionize the battery industry. Until then, high-quality LiFePO4 batteries, like those in EcoFlow Portable Power Stations, remain the most efficient and reliable option for everyday electronics, EVs, and renewable energy needs.