Sodium Batteries vs. Lithium Batteries: Current Status and Future of Solar Energy Storage Technology

I. Core Comparison: Four Key Dimensions of Sodium Batteries vs. Lithium Batteries

1.1 Raw Materials: Resource Endowment Shapes Long-Term Potential

Sodium batteries hold overwhelming advantages in terms of resource availability:

• Abundance & Pricing: Sodium accounts for 2.74% of the Earth’s crust, widely distributed in seawater and rock salt mines, with total reserves reaching approximately 2.7 trillion tons. Sodium carbonate is priced at only 3,000 RMB/ton. In contrast, lithium has a crustal abundance of just 0.0065%; lithium carbonate prices once soared to 600,000 RMB/ton and still remain at a high level of 80,000 RMB/ton, with significant price volatility.

• Material Composition: Sodium batteries do not require copper foil (low-cost aluminum foil is used instead). Their cathodes can utilize elements with abundant reserves (e.g., iron, manganese), and anodes are primarily made of hard carbon. Lithium batteries, however, rely on scarce or high-cost materials such as spodumene, cobalt (for NCM/NCA ternary systems), and copper foil—resulting in a 30%-50% higher share of raw material costs.

1.2 Cost: A Critical Competitive Edge in Energy Storage Scenarios

Cost is the key strength of sodium batteries in energy storage applications, evident in three aspects:

• Current Cost Gap: By 2025, the cell cost of sodium batteries has fallen to 0.3-0.5 RMB/Wh (layered oxide system), with the polyanion system even lower at 0.39 RMB/Wh. For comparison, lithium iron phosphate (LFP) batteries cost 0.5-0.8 RMB/Wh, while ternary lithium (NCM/NCA) batteries range from 0.8-1.0 RMB/Wh.

• Full-Life Cycle Advantage: In typical solar energy storage scenarios, the unit operating cost (RMB/Wh·year) of sodium batteries is significantly lower than that of lithium batteries. Particularly in peak-shaving and valley-filling scenarios with high charge-discharge frequency, this cost advantage can widen to over 40%.

• Cost Reduction Potential: With the roll-out of GWh-scale production lines, the share of auxiliary material costs for sodium batteries will drop further from 60%. A target cost of 0.2 RMB/Wh is expected to be achieved once large-scale production is realized.

1.3 Energy Density: Technical Limitations Restrict Application Boundaries

Currently, sodium batteries have an energy density of 150-200 Wh/kg—an improvement of 60% compared to 2020, but still significantly lower than LFP batteries (200-250 Wh/kg) and ternary lithium batteries (250-350 Wh/kg). This gap forces sodium batteries to occupy more space in large-scale long-duration energy storage projects, increasing system integration costs by 15%-20%.

However, breakthroughs have been made in R&D:

• New layered oxide cathode materials have pushed the laboratory energy density of sodium batteries to over 240 Wh/kg.

• Optimized mass production processes for hard carbon anodes are expected to extend cycle life from 1,000 to 3,000 cycles (at 80% capacity retention), approaching the performance of LFP batteries.

  
  

1.4 Safety: A Core Guarantee for Energy Storage Scenarios

Sodium batteries demonstrate superior safety performance:

• Their thermal decomposition temperature is over 150℃ higher than that of lithium batteries, with no risk of thermal runaway in the wide temperature range of -20℃ to 60℃. Only bulging (no fire) occurs in puncture and extrusion tests.

• This advantage makes sodium batteries naturally suited for outdoor solar energy storage stations (which often face extreme temperatures), cutting the capital expenditure (CAPEX) for fire-fighting systems by over 30%.

While lithium batteries have improved safety via technologies like ceramic separators and flame-retardant electrolytes, thermal runaway risk in NCM/NCA ternary systems has not been fully eliminated. Additionally, LFP batteries suffer a 40% capacity loss in low-temperature environments, making them less adaptable than sodium batteries.

II. The "Replacement" Debate: A Coexistence Pattern Under Scenario Differentiation

Sodium batteries will not fully replace lithium batteries; instead, they will form a complementary pattern based on scenario-specific needs. Below is their respective penetration paths and irreplaceable fields:

2.1 Penetration Path of Sodium Batteries

• Rapid Replacement in Advantageous Scenarios:In distributed solar energy storage (household/rural PV), low-temperature energy storage (outdoor power stations in northern China—cold-climate regions with temperatures as low as -20℃), and backup power scenarios, sodium batteries have already captured over 10% market share in 2025, with expectations to reach more than 35% by 2030.A typical example is the PV poverty alleviation projects in northwest China (initiatives using PV systems to support low-income rural communities): sodium battery systems have reduced the Levelized Cost of Electricity (LCOE) to 0.3 RMB/kWh—0.12 RMB/kWh lower than lithium battery systems.

• New Opportunities from Technical Breakthroughs:If sodium batteries achieve an energy density of over 250 Wh/kg, they could enter the large-scale PV power plant energy storage segment—a market currently dominated by LFP batteries (holding an 80% share).

2.2 Irreplaceability of Lithium Batteries

• Scenarios Requiring High Energy Density:In mobile energy storage (e.g., PV-powered vehicles) and long-duration energy storage (≥8 hours of discharge), lithium batteries remain the only viable option. For instance, in PV-supported energy storage projects above 10 MWh, lithium battery systems occupy 25% less floor space than sodium battery systems, aligning better with land intensification requirements.

• Industrial Chain Barriers:Lithium batteries have formed a complete industrial chain covering lithium mining, production, and recycling, with a global capacity of 2 TWh/year. In contrast, sodium battery capacity is only 50 GWh/year—insufficient to meet large-scale replacement needs in the short term.

III. Technology Outlook: Next-Generation Solar Energy Storage Directions

Future solar energy storage technologies will advance along three paths—sodium battery upgrades, cross-border integration, and disruptive technology reserves—to further improve efficiency and cost-effectiveness.

3.1 Sodium Battery Technology Upgrades

• Material Innovation:

Manganese-rich cathode materials can increase energy density to 280 Wh/kg.

Sulfide electrolytes can triple ionic conductivity, with mass production expected by 2027.

• Structural Innovation:

Laminated cell design pushes power density to over 3,000 W/kg, adapting to PV fast-charging needs.

Fluidization modification enables cycle life to exceed 10,000 cycles (at 80% capacity retention).

3.2 Cross-Border Integration Technologies

• Integrated PV-Storage Batteries:By integrating perovskite PV layers with sodium batteries, the comprehensive photoelectric conversion and energy storage efficiency reaches 25%—8% higher than traditional "PV panel + battery" systems.

• Sodium-Hydrogen Hybrid Energy Storage:Short-cycle energy fluctuations are stabilized by sodium batteries, while long-cycle energy storage is handled by hydrogen energy. This technology has been piloted at a 50 MW PV power plant in Australia, achieving a comprehensive system efficiency of 82%.

3.3 Disruptive Technology Reserves

• Solid-State Sodium Batteries:Using polymer electrolytes, their energy density exceeds 400 Wh/kg, with pilot production expected to start by 2030.

• Seawater Sodium Extraction for Energy Storage:Seawater is directly used as raw material for electrolytes, cutting raw material costs by 50%. Currently, the laboratory conversion rate has reached 92%.

IV. Conclusion: A Scenario-Specific Revolution Driven by Cost

Sodium batteries and lithium batteries are not mutually exclusive; instead, they will form a complementary pattern where "sodium batteries dominate the low-end segment while lithium batteries lead the high-end segment." By 2030, the solar energy storage market will present a three-way split:

• Ternary lithium batteries (for high-end mobile energy storage),

• LFP batteries (for large-scale long-duration energy storage),

• Sodium batteries (for distributed and special-environment energy storage).

The core of next-generation technological breakthroughs lies in balancing energy density and cost:

• Sodium batteries will narrow the performance gap with lithium batteries through material innovation;

• Lithium batteries will enhance added value via solid-state and intelligent development;

• Cross-border technologies (e.g., PV-storage integration, cross-medium energy storage) will open up new growth avenues for solar energy storage.