Solid State Batteries Vs. Lithium-Ion: Which One is Better?

Lithium-ion batteries have been powering our devices and electric vehicles for years, but solid-state batteries are now heralded as the next big thing. But how accurate is that claim?

Despite the hype, you can't buy a car with a solid-state battery today. While showing significant potential, there are still ways to go to make solid-state batteries commercially viable for EVs. Still, massive research and development investments aim to change that in the coming years.

In this article, we explore why solid-state batteries might become a better option than lithium-ion in the future, but first…

Table of Contents

• How Do Lithium-Ion and Solid-State Batteries Work?
• Solid State Batteries Current Challenges
• Key Comparisons
• Recent Breakthroughs and Innovations
• Which One is Better?

How Do Lithium-Ion and Solid-State Batteries Work?

Let’s break down the structure of both lithium-ion and solid-state batteries and then show the key differences.

Lithium-Ion Battery Structure

Lithium-ion batteries consist of the following key components:

• Anode (negative pole): Usually made of graphite
• Cathode (positive pole): Often composed of nickel, manganese, cobalt, or iron phosphate (LFP)
• Electrolyte: A liquid solution, typically liquid salt dissolved in an organic solvent
• Separator: Positioned between the anode and cathode, surrounded by liquid electrolytes

During charging and discharging, lithium ions move between the anode and cathode through the liquid electrolyte. While efficient, there are safety concerns with lithium-ion batteries because of the flammable liquid electrolyte.

Solid-State Battery Structure

Solid-state batteries have a similar structure but with one crucial difference:

• Anode: Often made of lithium metal or lithium alloy
• Cathode: Similar to lithium-ion batteries. Usually made from metal oxides (such as NMC - nickel, manganese, cobalt)
• Electrolyte: Solid, typically made from ceramics, polymers, or sulfides
• Separator: Often integrated with the solid electrolyte to maintain ion flow. Its role is to allow ion flow while preventing direct contact between the anode and cathode

This solid electrolyte is the key to many advantages solid-state batteries offer, including improved safety and stability.

Solid State Batteries Current Challenges

While there remain concerns about lithium shortages, lithium-ion batteries are widely available today with an established manufacturing infrastructure. Despite being a mature technology, ongoing research and development continue to improve lithium-ion battery performance, lifespan, and safety.

Solid-state batteries are still primarily confined to laboratories and small-scale prototypes. And, there are still some significant challenges that must be overcome before they become more mainstream.

High Production Costs

The materials used in solid-state batteries, particularly the solid electrolyte, are currently more expensive than those in lithium-ion batteries. The manufacturing process itself is more complex and requires specialized equipment.

Existing battery manufacturing equipment is designed for liquid electrolyte batteries and is not suitable for solid-state production. New, specialized equipment needs to be developed and produced at scale, which requires significant investment.

Technical Challenges

There are also several technical challenges that manufacturers are working hard to address:

• Crack Formation: 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.
• Ion Conductivity: While solid electrolytes offer safety benefits, achieving ion conductivity comparable to liquid electrolytes at room temperature remains a challenge.
• Scaling Up: What works in small, laboratory-scale batteries often faces new challenges when scaled up to the sizes needed for electric vehicles.

Despite these challenges, substantial investments are being made by major automotive and technology companies to overcome these hurdles. Many experts believe that solid-state batteries could become commercially viable within the next 5-10 years, revolutionizing energy storage for electric vehicles and other applications.

Key Comparisons

Energy Density

Lithium-ion batteries used in EVs typically have energy densities ranging from 160 Wh/kg (LFP chemistry) to 250 Wh/kg (NMC chemistry). Research is ongoing to improve these figures. For example, at Yokohama National University, they are exploring manganese in the anode to improve energy density of the LFP battery.

Solid-state batteries offer much higher energy density potential. Thin-film types can reach 300-800 Wh/kg, while bulk types are around 250-500 Wh/kg. Recent research by Mercedes and Factorial claims to have achieved 450 Wh/kg in a new solid-state battery type, which is 33% smaller and 40% lighter than comparable lithium-ion batteries.

Safety

The liquid electrolyte in lithium-ion batteries poses a risk of overheating and flammability, although the actual risks are often overstated.

 “We’re growing increasingly confident with each study that we can solve the safety and range issues in electric vehicles,” said Chunsheng Wang, professor of chemical and biomolecular engineering at the University of Maryland told NBC News.

Solid-state batteries, with their non-flammable solid electrolyte, significantly reduce fire risk and eliminate gas venting issues. They're also easier to control in terms of temperature.

Lifespan and Durability

Lithium-ion batteries degrade over time due to chemical reactions, resulting in a shorter lifespan. Solid-state batteries have the potential for a longer lifespan, but currently face challenges with crack formation in the solid electrolyte during charging and discharging cycles, which increases resistance.

Charging Speed

Lithium-ion batteries offer moderate to fast charging but are sensitive to temperature.

Solid-state batteries show promise for ultra-fast charging capabilities, with some prototypes reaching 80% charge in less than minutes. They're also less affected by temperature fluctuations.

Recent Breakthroughs and Innovations

Research institutions and companies are making strides in both lithium-ion and solid-state battery technologies:

• McGill University has increased porosity in solid electrolytes, reducing crack formation and improving durability.
• Nano-particle technology is being used to improve energy storage capacity and conductivity in both battery types.
• Tesla is focusing on NMC and LFP chemistry for lithium-ion batteries, aiming for a 15–20-year lifespan for EV batteries. However, with recent legislation regarding China-made electric vehicles, LFP batteries in North America are expected to become less popular for EVs but continue to be used for battery energy storage systems.

Continued R&D looks to improve both battery types. Solid-state batteries are expected to be commercialized around 2026-2027 with significant breakthroughs promising fast-charging, high-energy-density solutions for EVs. The world’s largest automaker, Toyota, said it plans mass production in 2027-2028 with a battery charging time of 10 minutes and a range of more than 620 miles.

Which One is Better?

The answer to this question depends on whether you evaluate batteries based on current needs or future potential.

Lithium-ion batteries are more robust and available now, but have some safety and lifespan concerns. Solid-state batteries are superior in terms of energy density, safety, and charging speed but are still in early development and expensive to produce.

As research continues and manufacturing processes improve, solid-state batteries appear poised to become the preferred choice for EVs if the remaining challenges can be solved. However, for now, lithium-ion batteries remain the practical choice for most applications.

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