Sodium-Ion Battery Patents Are Surging — Who Really Wins the Low-Cost Battery Era?

What Is in Focus: The Low-Cost Battery Race Shifts Toward “Water” and Cost

The contest in sodium-ion batteries (secondary batteries in which sodium ions, rather than lithium ions, shuttle between the electrodes) will be decided less by energy density than by the choice of cathode family and by who first secures rights over that family’s core problem. On April 21, 2025, at its first “Super Tech Day,” CATL unveiled the sodium-ion battery “Naxtra” and announced it as the world’s first mass-producible sodium-ion battery. Taking that announcement as a starting point, this article maps where the sodium-ion patent landscape is splitting.

Looking first at the industry situation, the biggest strength of sodium-ion batteries is that they avoid lithium’s price volatility and the risk of a concentrated supply chain. When CATL unveiled its sodium-ion energy storage system (ESS) “TENER Sodium” on June 22, 2026, it explained that sodium is about 1,000 times more abundant than lithium and stated that it had accumulated more than 1,600 patent families and over 200 granted patents in this field. In Korea, LG Energy Solution is reported to have been the first to move into sodium battery development, Samsung SDI is running lab-level R&D, and SK On has it listed among its next-generation candidates.

There are two sources of tension. First, sodium-ion batteries have lower energy density than lithium-ion, which limits their applications. Second, cathode materials are split into three families — layered oxide, Prussian blue, and polyanionic — and it has not yet been settled which family will become the standard. This article answers three questions: how does a sodium-ion battery work, what are the patents in the three cathode families fighting over, and which rights should planning and IP staff check first?

Basic Principle: A Wider Room for a Larger Guest

A sodium-ion battery works on the same principle as a lithium-ion battery. During charging, cations leave the cathode and are stored in the anode; during discharge, they move back. The difference is the size of the moving ion. Because a sodium ion (0.102nm) is larger than a lithium ion (0.076nm), it has difficulty entering graphite’s interlayer spacing (0.34nm), so the anode mainly uses hard carbon (non-graphitized amorphous carbon), which has a wider interlayer structure.

By analogy, the lithium ion is a small guest who fits even into a narrow corridor-style room, while the sodium ion is a large guest who catches on the threshold. The design of a sodium-ion battery therefore comes down to providing “a wide room a large guest can enter and leave” in both the cathode and the anode. The three cathode families build this room in different ways.

• Layered oxide: Sodium moves in and out between layers of metal oxide. Its structure resembles lithium-ion NCM (nickel-cobalt-manganese oxide) cathode material, making it easy to carry over existing process know-how.
• Prussian blue: Sodium moves in and out of the large empty spaces formed by an iron-cyanide framework. Raw-material cost is low, but water (crystal water) easily enters the crystal during synthesis, and this water becomes a factor that reduces cycle life.
• Polyanionic: A structure in which an anion backbone such as phosphate (PO₄) or pyrophosphate (P₂O₇) forms a rigid framework. This family puts structural stability first.

Low-temperature performance is cited as a signature strength of sodium-ion. CATL announced that the Naxtra passenger EV battery retains 90% of usable power even at minus 40°C. However, this is a figure announced by the manufacturer and may vary with cell design and test conditions.

Comparison: Position Versus Lithium-Ion and CATL’s Announced Figures by Generation

The two tables below preserve the figures from the original article while adding values confirmed by CATL’s official announcements.

Category	Sodium-ion battery	Lithium-ion battery (NCM)
Radius of moving ion (nm)	0.102	0.076
Main anode material	Hard carbon	Graphite (interlayer 0.34nm)
Cell energy density (Wh/kg)	140-200	250-300 range
Raw-material abundance	Abundant in seawater and the earth’s crust	Concentrated sources, price volatility
Low-temperature performance	Operation at minus 40°C announced	Relatively larger power drop at low temperature

What this table says: Sodium-ion is at least about 50Wh/kg below NCM in energy density, but it differentiates itself on raw-material abundance and low-temperature performance. In other words, its arena is applications where cost and cold performance matter more than high-performance EVs.

Category	First-generation sodium-ion (2021)	Naxtra (2025)
Announcement date	2021-07-29	2025-04-21
Energy density (Wh/kg)	Up to 160	175
Disclosed cathode material	Prussian white	Not specified in the official announcement
Low-temperature performance	Over 90% capacity retention at minus 20°C	90% of usable power retained at minus 40°C
Other	80% charge in 15 minutes at room temperature; next-gen target above 200Wh/kg	Over 10,000 cycles; 500km range (announced)

What this table says: CATL announced that it raised energy density from 160 to 175Wh/kg over four years, but it has not yet reached the above-200Wh/kg target it stated in 2021. It is also notable that the Naxtra announcement did not specify the cathode family that was disclosed for the first generation.

Patent Perspective: An Expired Early Patent and Live “Crystal Water” Patents

Where KR101546877B1 actually sits: KR101546877B1 (“Cathode Material for Sodium-Ion Battery, Method for Manufacturing the Same, and Sodium-Ion Battery Comprising the Same”), introduced in the original article as an early domestic patent, lists the Korea Advanced Institute of Science and Technology (KAIST) as applicant on Google Patents, with inventors Choi Jang-Wook, Lim Soo-Yeon, Jung Yoo-Sung, and Kim Hee-Jin. It was filed on June 12, 2013, published on December 22, 2014 (KR20140144912A), and granted on August 25, 2015. Its legal status is shown as expired for non-payment of annual fees (Expired – Fee Related).

Claim 1 claims a sodium-ion battery cathode material containing Na₇V₄(P₂O₇)₄PO₄, a vanadium-based pyrophosphate-phosphate. In other words, this patent belongs not to the layered-oxide family the original article implied but to the polyanionic family. The interpretation that “early domestic patents concentrated on the layered-oxide family” is therefore hard to base on this patent and needs to be checked against separate filing statistics.

In the Prussian blue family, the issue is water: Rights in the Prussian blue family have accumulated around how the water in the crystal is handled. We checked two representative patents.

• US9478798B2 (filed by Sharp Laboratories of America; current owner Sharp Corp): priority date March 28, 2012, granted October 25, 2016, Active, anticipated expiration March 28, 2032. Claim 1 claims a cathode in which the zeolitic water (water in the lattice interstices) content of the hexacyanometallate particles is zero while bound water remains.
• US11424450B2 (filed by CATL; current owner CATL’s Hong Kong entity): priority date May 18, 2017, filed November 14, 2019, granted August 23, 2022, Active. Claim 1 claims a Prussian blue analogue in which part or all of the coordinated water is replaced by a neutral ligand such as acetonitrile, ammonia, carbon monoxide, or pyridine. The European patent in the same family, EP3614468B1, was granted on August 9, 2023.

Insight: an expired patent is a “free-to-practice zone,” while crystal-water patents are a “toll section.” The fact that KR101546877B1 has lapsed means that the likelihood of rights being asserted in Korea over this composition itself has fallen. By contrast, in the Prussian blue family, control of crystal water — which governs cycle life — is covered by live granted rights under different approaches (removing water vs. ligand substitution). The winner of the low-cost battery era may be not the side that picked the cheapest material, but the side that secured rights over how to solve that material’s core problem.

Avoidance points: Because the wording of US11424450B2 requires a structure in which a neutral ligand L replaces coordinated water, a process that lowers moisture only through drying and heat treatment without ligand substitution may lack an element of this claim. Conversely, that route can come closer to the “zero zeolitic water” limitation claimed by US9478798B2, so the two patents need to be compared at the same time.

Design-around scenario (counterargument): A design that leaves a small amount of zeolitic water rather than reducing it completely to zero may fall outside the literal scope of US9478798B2. However, if the residual amount is at the level of the measurement limit, the possibility of infringement may be disputed over the doctrine of equivalents or the interpretation of the measurement method. Ultimately, the avoidance potential depends on how the moisture measurement method and claim construction interact.

Limits and Outlook

Because of its energy-density limits, the sodium-ion battery is more likely to gain a foothold first in ESS, low-cost compact EVs, and power tools than as a primary EV battery. CATL, too, set a target of 1GWh cumulative shipments by the end of 2026 when it unveiled its ESS product on June 22, 2026, and on February 5, 2026 it announced a sodium-ion passenger-vehicle collaboration with Changan. Following this split in applications, the patent landscape is dividing into a layered-oxide family that reuses lithium-ion technology and a low-cost Prussian blue/polyanionic family.

The optimistic outlook is that, as production scale grows, sodium-ion will replace part of the demand for LFP (lithium iron phosphate) batteries. There is also a counter-scenario. If lithium prices stay low, sodium-ion’s cost advantage shrinks, and LFP, with its higher energy density, may continue to hold the same applications. In that case, sodium-ion could remain in a low-temperature, high-safety niche.

A strategic alternative is to map the “core-problem patents” of each family before committing to a single cathode family. Because rights cluster at different points in each family — air stability for layered oxides, crystal water for Prussian blue, cost and conductivity for polyanionics — separating live and expired rights by problem can reduce the FTO (freedom-to-operate) burden when switching materials. Which side becomes the standard will likely be gauged by the cycle-life data and related patents that accumulate over the next two to three years.

Practical action: Planning and IP staff reviewing Prussian-blue-family sodium-ion cells or materials should first confirm how the supplier’s cathode material removes moisture (a drying process or ligand substitution), and organize the result into an element comparison chart placed side by side with claim 1 of US9478798B2 and US11424450B2.

Items requiring verification

• The cathode family actually used in Naxtra (not specified in CATL’s official announcement)
• Filing statistics supporting the interpretation that early Korean sodium-ion patents concentrated on the layered-oxide family
• Official materials from LG Energy Solution, Samsung SDI, and SK On on the stage of each company’s sodium-ion development
• The degree to which Chinese companies concentrate filings of synthesis-process patents for crystal-water control (counts by year)
• Whether a Korean family member of US11424450B2 has been filed or granted

Sources

1. Google Patents, KR101546877B1 – Cathode material for sodium-ion battery, method for manufacturing the same, and sodium-ion battery comprising the same (KAIST)
2. Google Patents, US11424450B2 – Prussian blue positive electrode material, preparation method therefor, and electrochemical energy storage device (CATL)
3. Google Patents, EP3614468 – European patent in the same family (CATL)
4. Google Patents, US9478798B2 – Prussian blue analogue electrodes without zeolitic water content (Sharp)
5. CATL press release, CATL Unveils Its Latest Breakthrough Technology by Releasing Its First Generation of Sodium-ion Batteries (2021-07-29)
6. CATL press release, Naxtra Battery Breakthrough & Dual-Power Architecture (2025-04-21)
7. CATL press release, CATL and CHANGAN Launch World’s First Mass-Production Sodium-Ion Passenger Vehicle (2026-02-05)
8. CATL press release, CATL Debuts World’s First Field-Validated Sodium-Ion BESS (2026-06-22)

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