Solid-State Battery vs Lithium-ion

Solid-state batteries (SSBs) differ from conventional lithium-ion batteries (LIBs) in terms of both their components and fundamental design features. Instead of a liquid electrolyte, they use a solid electrolyte to conduct lithium ions between electrodes. Because there is no liquid medium, a polymer separator is not required to prevent short circuiting. Additionally, the enhanced thermal and electrochemical stability of solid electrolytes, especially compared to flammable liquid electrolytes, enables the use of electrode materials with wider electrochemical potential windows, including lithium metal anodes and high-voltage cathodes. Currently lihtium-ion batteries have more efficient charging technology which facilitates faster charging. It is also cheaper and more scalable. As solid-state battery technology develops, can it out perform LIBs?

Solid-state Battery vs Lithium-ion Battery Component Comparison

Solid-state and lithium-ion batteries differ in several key components, particularly in the state of the electrolyte and the types of compatible electrodes. The comparison below highlights these key differences and the materials commonly used in each type of battery technology.

Component	Solid-State Battery		Lithium-ion Battery
Electrolyte	Solid Electrolyte More stable - better safety No evaporation or leaking		Organic Liquid electrolytes + Lithium Salts Forms solid electrolyte interphase at the anode with risk of excessive and uncontrolled growth Risk of electrolyte evaporation and leakage
Electrode Materials	Cathode – lithium-based oxides and phosphates + higher voltage cathode materials Anode – metallic lithium, graphite/silicon		Cathode – lithium-based oxides and phosphates Anode – graphite/silicon or lithium-based (LTO)
Interface	Solid-solid contact Smaller contact area Higher interfacial resistance between electrolyte and cathode active materials Grain boundaries with high resistance		Solid-liquid contact Liquid electrolyte wets entire solid electrode surface Ensures intimate contact, maximizing the area for lithium-ion transfer

Electrolyte

The state of the electrolyte is the major difference between solid-state and lithium-ion battery technology:

The biggest difference between the two battery types is that one uses a solid electrolyte and the other uses a liquid. This change affects almost everything; how fast the battery works, how safe it is, how much energy it can store, and what materials it can use. Solid electrolytes can handle higher temperatures and voltages, and they work better with lithium metal electrodes.

Electrode Materials

Anode Materials

Anode active materials can be the same in both solid-state and lithium-ion batteries. Graphite is typically used in lithium-ion batteries but solid-state batteries have the potential to accommodate metallic lithium anodes.

Cathode Materials

Like the anode, the same cathode active materials can feature in both solid-state and lithium-ion batteries. However, high-voltage lithium-based cathodes are more commonly used in solid-state batteries because the solid electrolyte offers greater stability at higher voltages. Cathode coatings are often applied to further enhance interfacial stability and overall battery performance.

Lithium Nickel Manganese Oxide (LNMO) Powder

From $189

Lithium Iron Phosphate (LiFePO₄) Powder

From $208

Lithium Nickel Manganese Cobalt Oxide (NMC811) Powder

From $208

Lithium Manganese Oxide (LMO) Powder

From $215

Lithium Cobalt Oxide (LiCoO₂) Powder

From $195

Electrolyte-Electrode Interface

A key way in which solid phase electrolyte differs from liquid electrolyte is the interface created between the electrolyte and electrode. Liquids can easily wet the whole electrode surface, ensuring good interactions between the electrolyte and electrode. This facilitates excellent ionic conductivity.

Solid electrolyte on the otherhand suffers from a smaller contact area with electrodes. Common issues faced by solid electrolyte is high internal resistances at the interface which can be difficult to diagnose. Some explanations include chemical incompatibility, electrochemical reaction and mechanical issues which disrupt lithium ion flow. Coating electrodes with an oxide barrier layer has been employed to suppress development of extreme interfacial resistance and enable high-rate cycling.

Solid-state Battery vs Lithium-ion Battery Feature Comparison

The difference in features of solid-state and lithium-ion batteries arise from their components. The key differences in features are highlighted below:

Feature	Solid-State Battery		Lithium-ion Battery
Cycle Life	Lower - Poorer interface interactions mean electrochemical stability is reduced therefore cycle life typically lower		Higher - Better interface interactions mean electrochemical stability is increased therefore cycle life typically higher
Energy Density	Higher - 250 - 800 Wh/kg		Lower - 160 - 250 Wh/kg
Size	Smaller No need for polymer separator Lithium metal anodes are typically smaller than graphite		Larger Separator is needed to protect from short circuiting Graphite anode is quite large in comparison to lithium metal anodes.
Charging Speed	Slower - lower ionic conductivity and poor electrolyte-electrode interface contact means low critical current density and slow charging speeds.		Faster - Liquid electrolytes typically have high ionic conductivities with better contact between the electrode and electrolyte interface.
Electrochemical Stability	Broader Window - Can resist oxidation or reduction over a broader voltage range		Narrow Window - The voltage range for resisting oxidation and reduction is smaller
Thermal Stability	Higher - Solid electrolyte has a higher melting point and is less likely to burn		Lower - Risk of thermal runaway
Mechanical Strength	High - Can suppress lithium dendrite growth but it is still possible especially along void and grain boundaries.		Low - Lithium dendrites can grow through the electrolyte and short the cell
Safety	More Safe - Electrolyte is more stable and less likely to burn		Less Safe - Issues of electrolyte leakage, overheating and fires
Cost	More expensive - New electrolyte technology and high performance electrode materials.		Cheaper - Mature electrolyte and electrode technology.
Scale Up	Limited feasibility currently		Established

Cycle Life

Currently solid-state batteries show lower cycler life than lithium-ion batteries due to a lack of development in optimizing device components. One of the most significant issues is the formation of cracks in the solid electrolyte during charging cycles. These cracks can lead to increased internal resistance and reduced battery performance over time.

Energy Density and Size

Solid-state batteries are typically more energy dense than lithium-ion batteries because they can use lithium metal anodes, which offer much higher capacity than graphite. Their solid electrolytes also enable the use of higher-voltage cathodes and support thinner, more compact designs. Together, these features allow more energy to be stored in the same volume or weight, making solid-state batteries ideal for applications where space and efficiency matter.  

Charging Speed

Solid-state batteries typically charge more slowly due to lower ionic conductivity and limited contact between the solid electrolyte and electrodes. However, they have potential for faster charging in the future because they can safely use lithium metal anodes and high-voltage cathodes, which could enable higher energy transfer rates. In contrast, lithium-ion batteries charge faster today, due to their liquid electrolytes that offer high ionic conductivity and efficient electrode contact.

Safety and Stability

Solid-state batteries offer broader electrochemical stability, higher thermal stability, and greater mechanical strength, which helps suppress dendrite growth and reduce fire risk. Overall, they are considered safer and more stable, though lithium dendrite growth is still possible. Lithium-ion batteries, have narrower stability windows, lower thermal resistance, and are more prone to dendrite formation, leakage, and thermal runaway, making them less safe in comparison.

Cost and Scale Up

Solid-state batteries are currently more expensive due to the use of new materials and manufacturing processes, and they face challenges in large-scale production. Lithium-ion batteries are cheaper and easier to scale, benefiting from decades of development, mature supply chains, and well-established manufacturing infrastructure.

Why does replacing a graphite anode with a lithium metal anode improve energy density?

Replacing graphite anodes with metallic lithium results in a dramatic increase in energy density (40-50%). Lithium metal anodes are able to store more energy per unit of volume or mass which is shown in properties such as high volumetric (2093 mAh cm⁻³) and gravimetric specific capacity (3862 mAh g⁻¹). Metallic lithium has the lowest reduction potential (−3.05 V vs SHE.) which also directly contributes to high energy density. The lower the reduction potential of an anode the higher the cell voltage with a given cathode. Energy density is also linked to cell voltage, therefore the higher the cell voltage the higher the energy density of the cell:

Gravimetric Energy Density

The low reduction potential of a lithium anode increases the likelihood of lithium plating and uncontrolled solid-electrolyte interphase (SEI) formation. This arises from a mismatch in electrochemical potential between the lithium metal anode and the liquid electrolyte. As a result, the electrolyte components undergo spontaneous reduction reactions at the anode surface, leading to further decomposition and the formation of an unstable or non-uniform SEI layer.

Combining Solid-State and Lithium-Ion Technologies

Integrating features from both solid-state and conventional lithium-ion batteries represents a promising direction for advanced energy storage systems. For example, certain lithium polymer batteries utilize a gel polymer electrolyte, which is composed of a solid polymer matrix infused with liquid electrolyte and lithium salts. This hybrid configuration combines the high ionic conductivity and effective electrode wetting of liquid electrolytes with the mechanical robustness and improved safety characteristics of solid polymers.

Cathode Active Materials

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