The First Stage for a Lithium-Free Battery — Why Sodium-Ion Is Headed for the Data Center UPS

What’s the Story: Why the First Stage Is UPS, Not EVs

Sodium-ion batteries entering data center UPS (uninterruptible power supply) systems first is not a marketing choice but an order set by chemistry. The next-generation card that Korea’s three battery makers all mentioned in their Q2 2026 earnings briefings was not solid-state but sodium-ion, and specifically for UPS. This article lays out, in the order of chemistry, comparison, and patents, why a battery that is heavier and lower in energy density than lithium is heading to UPS now, and of all applications.

Here is the situation. The spread of AI data centers has driven a surge in demand for ESS, UPS, and BBU (battery backup units attached to server racks) batteries, and LFP (lithium iron phosphate) has effectively come to dominate the chemistry in this market. The three Korean makers have said they are developing sodium-ion as their next-generation UPS product, and LG Energy Solution has reportedly signaled mass production in 2027. China is ahead: CATL unveiled its first-generation cells on July 29, 2021, and launched its sodium-ion brand “Naxtra” on April 21, 2025.

The tension is in the supply chain. Most of the LFP value chain sits in China, and lithium prices swing with market conditions. That raises the questions this article answers: can a battery made without lithium replace part of this stationary (installed in a fixed location) market, and what patents lie along that path?

Basic Principle: What Happens When You Swap Lithium for Sodium

On the periodic table, sodium sits directly below lithium. The operating principle is the same: ions shuttle between the cathode and anode to charge and discharge. What differs is the ion’s size and character. Sodium ions are larger and heavier than lithium ions, so less energy is stored in the same volume. That is why energy density generally sits one tier below LFP.

By analogy, it is like parking mid-size cars instead of compact cars in the same lot. With fewer spaces, total capacity (energy density) drops, but it opens room to redesign the lot. Sodium-ion gains three things by changing the chemistry.

• Anode: Sodium ions cannot intercalate stably between graphite layers the way lithium can, so hard carbon, an amorphous (irregular crystal arrangement) carbon, is used instead
• Current collector: Lithium cells must use copper foil at the anode (because lithium alloys with aluminum at low potential), but sodium does not alloy with aluminum, so both electrodes can use aluminum foil. This lowers cost versus copper, and cells can be stored and transported fully discharged to 0V, raising handling safety
• Low-temperature and thermal stability: These tend to be better, making it more robust in outdoor, non-climate-controlled environments

In short, it is a trade: give up energy density, get a lower cost ceiling, safety, and cold-weather performance. Three cathode chemistries are competing: layered oxides, Prussian blue analogues (open frameworks in which iron, manganese, and other metals are linked by a cyanide skeleton), and polyanionic compounds.

Comparison: LFP and Sodium-Ion from the Stationary Market’s Point of View

Item	LFP	Sodium-Ion
Energy density	High (sufficient by stationary standards)	Low — weight/volume penalty
Key raw material	Lithium (price volatility, geographic concentration)	Sodium (abundant, low-cost)
Current collector	Copper foil required at the anode	Aluminum foil possible at both electrodes
Full-discharge storage/transport	Not possible (over-discharge damage)	0V storage possible
Low-temperature/thermal stability	Good	Tends to be better
Mass-production maturity	Global standard	Early stage — China ahead, Korea entering

What this table says: Sodium-ion’s weakness (energy density) is the item that hurts least in the stationary market, and its strengths (cost ceiling, full-discharge handling, low temperature) are the items UPS values most.

To supplement the qualitative comparison with numbers, we compiled the cell figures disclosed by the front-runner, CATL. All are company-announced values, not third-party verified figures.

Item	First-generation sodium-ion cell (announced 2021-07-29)	Naxtra (announced 2025-04-21)
Cell energy density (Wh/kg)	Up to 160	175
Low-temperature performance	Over 90% capacity retention at -20°C	90% usable power retained at -40°C
Operating temperature range (°C)	Not confirmed in public materials	-40 to +70
Cathode and anode materials	Prussian white cathode, porous hard-carbon anode	Not confirmed in public materials
Other	80% SOC in 15 minutes at room temperature; AB battery system mixed with lithium-ion	Company describes energy density as comparable to LFP

What this table says: By CATL’s figures, cell energy density rose from 160 to 175 Wh/kg over four years, while the low-temperature benchmark moved down from -20°C to -40°C. The energy-density gap is narrowing, but the most prominent differentiator is still on the low-temperature side.

Patent Perspective: Rights Hinging on Cathode Materials and Moisture Control

The axes of sodium-ion patent competition are cathode chemistry and the raw materials (biomass, resin, and others) and precursor processing for hard-carbon anodes. China is clearly the front-runner: CATL brought out commercial cells and a brand first, and is building out the materials value chain vertically the same way it did with LFP. We confirmed two of CATL’s US granted patents on Google Patents.

• US10818924B2 (title “Positive electrode plate, preparation method thereof and sodium-ion battery”): original assignee CATL, priority date October 30, 2017, granted October 27, 2020, Active, anticipated expiry December 16, 2038. The current assignee is listed as CATL’s Hong Kong entity
• US11196046B2 (layered-oxide cathode active material): original assignee CATL, priority date January 11, 2019, granted December 7, 2021, Active, anticipated expiry January 2, 2040. Claim 1 limits the composition Na₀.₆₇Mn_xA_yB_zO_2+δ (0<x<1, 0<y<0.1, etc.)

Claim summary (restated): Claim 1 of US10818924B2 claims a positive electrode plate with a positive active material film on a positive current collector, where the film contains a Prussian blue analogue of composition A_xM[M'(CN)₆]_y (0<x≤2, 0<y<1) and has a water content of 100–5000 μg per gram of film. Here A is an alkali or alkaline-earth metal ion, and M and M’ are transition metals.

Insight: For the Prussian blue family, FTO may be decided not by the “composition sheet” but by the “drying process records.” Prussian blue analogues have a structure that readily holds water within the crystal, so moisture control is a key performance variable. US10818924B2 claims precisely this water content as a numerical range, creating a structure in which the same composition can fall inside or outside the scope of rights depending on drying conditions. Infringement risk may therefore depend less on cathode composition than on the electrode drying process and the moisture measurement method (timing and technique).

Avoidance points: Literally, drying the film further to below 100 μg/g, or using a cathode without a cyanide framework such as layered oxides or polyanionic compounds, can keep distance from this claim. US11196046B2 likewise limits a narrow composition window, such as Na 0.67 and the Mn ratio, so layered oxides outside that window may fall outside its literal scope.

Design-around scenario (rebuttal): However, ultra-drying below 100 μg/g raises process cost, and re-absorption of moisture during cell assembly and storage could bring the water content back into range, leaving room for disputes over proof. Avoiding the composition window may also mean accepting performance loss. In the end, an economic judgment comparing the cost of avoiding numerically limited claims against licensing costs is needed, and whether the boundary values of the numerical limits hold up against prior art is a separate matter for review.

There is a rebuttal on the market side too. Sodium-ion’s economics are a relative-price argument that is maximized “when lithium is expensive.” In a phase where lithium prices stay low, it is hard to beat LFP, which has already completed its economies of scale, on cost, and sodium-ion cell unit costs at the small-production stage could actually run higher than LFP’s. In other words, sodium-ion’s winning case is not “it’s cheap now” but something closer to insurance value: a structurally lower price ceiling and a supply chain decoupled from lithium and from any single country.

Limitations and Outlook

The optimistic scenario is that as sodium-ion builds references in UPS and BBU and the hard-carbon and electrolyte supply chain matures to ton-scale volumes, it takes over stationary segments such as outdoor, cold-climate, and safety-regulation-tightened zones. There is an opposing scenario as well. If the low-lithium-price phase drags on and LFP costs keep falling, sodium-ion may fail to secure the volume needed to ride its learning curve and stay stuck in a niche. On top of that, if key cathode patents are concentrated among Chinese front-runners, Korean companies may have to clear two entry barriers — volume and rights — at the same time.

A strategic alternative is to decide the cathode chemistry together with the patent landscape: choosing the branch among Prussian blue, layered oxides, and polyanionic compounds where rights are less densely packed, or building an in-house portfolio first in materials such as hard-carbon precursors, where the rights landscape has not yet settled. The fork in the road is volume, not chemistry, and the specs and unit cost of Korean mass-production products due in 2027 will be the first answer sheet.

Practical action: Professionals planning sodium-ion UPS products should tabulate the composition of their intended cathode material and measured electrode moisture against the numerical ranges in the claims of US10818924B2 and US11196046B2, and check whether cell supply contracts include patent warranty (indemnity) clauses.

Items requiring verification

• The original statements on sodium-ion UPS made by the three Korean battery makers in their Q2 2026 earnings briefings
• LG Energy Solution’s 2027 mass-production schedule for sodium-ion products and the specifications of the target products
• The actual start of Naxtra mass production and the cathode and anode materials used
• Status of the Korean and Chinese family members of US10818924B2 and US11196046B2
• Public data comparing sodium-ion and LFP cell unit costs

Sources

1. CATL press release, CATL Unveils Its Latest Breakthrough Technology by Releasing Its First Generation of Sodium-ion Batteries (2021-07-29)
2. CATL press release, Naxtra Battery Breakthrough & Dual-Power Architecture: CATL Pioneers the Multi-Power Era (2025-04-21)
3. Google Patents, US10818924B2 – Positive electrode plate, preparation method thereof and sodium-ion battery
4. Google Patents, US11196046B2 – Positive active material, preparation process thereof, sodium ion battery and apparatus containing the same