Sodium-ion batteries are emerging as a cost-effective and sustainable alternative to lithium-ion technology. With advances in cathodes, anodes, and electrolytes, they offer improved safety, wider temperature stability, and the potential to support future electric vehicle energy needs.

Sodium-ion batteries are quickly gaining attention as a more affordable and eco-friendly alternative to lithium-ion batteries especially for personal electric vehicles. This overview breaks down the latest progress in sodium-ion technology, covering everything from electrode materials to electrolyte systems, safety improvements, and real-world performance.

Sodium is far more abundant and geographically widespread than lithium, making it cheaper, easier to source, and more environmentally sustainable. On top of that, sodium-ion batteries offer better thermal safety and perform reliably across a wide temperature range.

Still, they're not perfect. Lower energy density, shorter cycle life, and underdeveloped supply chains remain challenges. But ongoing innovations—like high-voltage cathodes, hard carbon anodes, and advanced polymer electrolytes—are steadily improving performance.

This review explores whether sodium-ion batteries can realistically replace, or at least complement, lithium-ion batteries in EVs. By comparing both technologies, we uncover how sodium-ion advancements could help meet future energy storage demands while reducing dependence on scarce lithium resources.

Introduction

Electric vehicles (EVs) are a major step toward reducing global emissions, and their performance largely depends on the batteries powering them. Today, lithium-ion batteries dominate the EV landscape because they deliver high energy density and have been commercially optimized for years.

But lithium-ion technology isn't without issues. Lithium mining raises ethical and environmental concerns, and the global lithium supply chain is vulnerable to price fluctuations and geopolitical tensions. This has sparked interest in alternatives—and sodium-ion batteries are one of the most promising candidates.

Sodium is far more abundant, evenly distributed, and stable than lithium. Plus, sodium-ion batteries share similar electrochemistry with lithium-ion batteries, making them compatible with existing battery manufacturing processes. Their lower energy density is still a drawback, but sodium-ion technology can complement lithium-ion batteries or even replace them in certain EV segments, especially where cost and safety are priorities.

This review brings together the latest research to evaluate whether sodium-ion batteries can genuinely support or replace lithium-ion batteries in the EV sector.

Sodium vs. Lithium: How Do They Stack Up?

Lithium-ion batteries have decades of development behind them, with billions invested in research, factories, and supply chains. But the world's growing demand for lithium, combined with geopolitical instability, is prompting companies to explore alternatives.

Lithium-Ion: The Current Standard

Lithium-ion batteries are popular for good reasons:

• High energy density: 250-300 Wh/kg


• Long cycle life: 500-1000 cycles


• Low self-discharge

These strengths make them ideal for smartphones, laptops, and EVs. However, there are downsides:

• Safety issues: They use flammable electrolytes that can cause thermal runaway


• Capacity fade: Cathodes degrade over time, causing 12-24% loss


• Geopolitical risks: A large share of lithium comes from regions like Chile, where policy changes can impact global supply and pricing


• Lithium carbonates have seen extreme price swings—from $6,000 per ton (2020) to $70,000+ (2022)—before stabilizing between $10,000-$25,000 in 2024.

Sodium-Ion: The Rising Contender

Sodium-ion batteries offer several advantages:

• Elemental abundance: Sodium is ~1,000 times more common than lithium


• Lower cost: Sodium-ion cells currently cost $80-$110 per kWh, cheaper than lithium-ion


• Better thermal stability: More resistant to overheating


• Wider temperature range: Works from -30°C to 60°C

On the flip side, sodium-ion batteries still struggle with:

• Lower energy density: 100-160 Wh/kg


• Shorter cycle life


• Immature recycling and supply chains

Companies like CATL and Faradion are driving large-scale development, but sodium-ion capacity remains far behind lithium.

Cathode Innovations: Boosting Sodium-Ion Performance

Cathodes play a huge role in determining a battery's energy density and stability. Researchers are exploring several promising cathode materials for sodium-ion batteries:

High-Voltage Fluorophosphates (A₂MPO₄F)

These materials deliver:

• 300 mAh/g capacity


• Over 1,000 Wh/kg energy density


• Operating voltage ≥5V

They are considered next-generation cathode candidates, though synthesis processes are still being optimized.

Sodium Vanadium Phosphate (Na₃V₂(PO₄)₃)

Strengths:

• Stable structure


• Fast sodium diffusion

Weakness:

• Poor conductivity (improved through carbon coating, doping, and porous structures)

Sulfate-Based Cathodes (Na₂Fe₂(SO₄)₃)

These offer high voltage and use abundant elements—making them low-cost and sustainable.

Prussian Blue Analogues (PBAs)

PBAs are one of the hottest areas of research thanks to:

• Open frameworks for fast Na⁺ movement


• Good cycling capability


• Low cost

However, they face challenges like:

• Structural instability


• Water content issues


• Vacancy formation

Scientists are addressing these issues using coatings, defect engineering, and doping (e.g., K⁺, Ni, Co, Cu, Cr).

Anode Advancements: Making Sodium Storage More Efficient

Anodes determine how much charge a battery can store and how long it lasts. Sodium-ion anode research focuses on improving cycle life, capacity, and structural stability.

Transition Metal Sulfides (e.g., WS₂)

Pros:

• Very high theoretical capacity

Cons:

• Large volume expansion during cycling


• Low conductivity

Solutions include nanostructuring and carbon-based composites.

Phosphorus-Based Anodes (e.g., Black Phosphorus)

Pros:

• Very high capacity

Cons:

• Severe volume changes

Researchers are testing nanoscale designs and carbon hybrids to stabilize them.

Carbon-Based Anodes (Hard & Soft Carbon)

These are currently the most commercially viable sodium-ion anodes.

Hard Carbon

• Capacity: 250-400 mAh/g


• Stores sodium through adsorption, interlayer intercalation, and nanopore filling


• Flexible structure helps keep cycling performance stable

Soft Carbon

• Lower capacity (150-250 mAh/g)


• Can be enhanced through nitrogen doping or conductive additives

Graphite, commonly used in lithium-ion batteries, doesn't work well for sodium because its interlayer spacing is too small.

Electrolytes: Ensuring Smooth Sodium Transport

Electrolytes allow sodium ions to move between electrodes. Several types exist, each with benefits and limitations.

Liquid Electrolytes

Pros:

• High ionic conductivity


• Fast charging


• Excellent electrode compatibility

Example: NaPF₆

Cons:

• Flammable organic solvents


• Higher risk of thermal runaway

Solid-State Electrolytes

Pros:

• Non-flammable


• Safe and stable


• No leakage

Typical conductivity: 10⁻⁵ to 10⁻³ S/cm (lower than liquids)

Newer ceramics and sulfides are improving conductivity and stability.

Polymer Electrolytes

Pros:

• Lightweight, flexible, easy to process


• No leakage


• Good safety profile

Cons:

• Lower room-temperature conductivity

Gels (GPEs) and solid polymer systems (SPEs) are being enhanced with nanofillers like SiO₂ and TiO₂.

Composite Electrolytes

Hybrid systems combining polymers + ceramics offer the best of both:

• High ionic conductivity


• Good flexibility


• Better thermal stability

These are emerging as a strong candidate for future sodium-ion EV batteries.