Can We Go Without Graphite? — The Dual-Track Strategy of Lithium Metal and Hard Carbon

What’s the story: two paths away from graphite

The move to replace graphite anodes is not converging on a single substitute; it is proceeding along two tracks, lithium metal at the premium end and hard carbon at the entry-level end. The two materials differ in the very way they eliminate graphite. Lithium metal removes the “house (host)” that receives lithium altogether, while hard carbon keeps carbon but switches to disordered, non-graphitic carbon and moves the battery chemistry itself to sodium-ion.

Looking at the industry situation, graphite accounts for more than 90% of the anode material market. Supply-chain regulation has been layered on top of this. China’s Ministry of Commerce and General Administration of Customs issued an announcement on October 20, 2023 that, from December 1, 2023, placed high-purity, high-strength, high-density artificial graphite materials and natural flake graphite products, including spheroidized graphite and expanded graphite, under export licensing. Since spheroidized graphite is a precursor material for anodes, the measure directly touched the battery industry. Regional supply-chain rules such as the U.S. IRA (Inflation Reduction Act) and Europe’s CRMA (Critical Raw Materials Act) are also pushing the discussion of moving away from graphite.

The tension lies in whether the substitutes are ready. Lithium metal offers overwhelming capacity but still faces safety challenges, and for hard carbon, mass-production facilities are only just being set up even in Korea. This article answers three questions. How do the two candidates differ from graphite in principle, how far have they come, and what rights structures should be examined from a patent standpoint?

Basic principle: a bookshelf, a bare floor and a sponge

Graphite is a structure in which carbon atoms are stacked neatly in sheets, and lithium ions are stored by slipping in between the sheets. By analogy, it is a bookshelf with fixed slots. Because the number of slots is fixed, its theoretical storage capacity has a clear ceiling of 372 mAh per gram.

Lithium metal clears away the bookshelf and piles lithium directly on a bare floor. A 2015 paper by Qian et al. in Nature Communications gives lithium metal’s theoretical specific capacity as 3,860 mAh/g and its potential as −3.040 V versus the standard hydrogen electrode, describing it as an “ideal anode”. That is about 10.4 times graphite’s value. However, the same paper points out that dendrite growth (lithium growing like branching crystals) and limited Coulombic efficiency (the ratio of charge discharged to charge put in) have prevented practical use. Piling on a bare floor means it does not stack evenly but spikes upward, which is why solutions are being sought together with solid-state electrolytes and interfacial engineering.

Hard carbon is closer to a wad of crumpled paper or a sponge. A 2023 paper by Tang et al. in Nature Communications describes hard carbon as a structure of randomly oriented, curved and defective graphene nanosheets with a large interlayer distance. Whereas graphite’s sodium storage capacity is limited because sodium-graphite intercalation compounds are unstable, hard carbon holds sodium in its wide interlayers and closed pores. The paper states in particular that closed pores play a key role in the low-voltage plateau capacity. The same paper describes hard carbon’s typical specific capacity as about 300 mAh/g.

Comparison: capacity, challenges and readiness

Category	Graphite	Lithium metal	Hard carbon
Target battery	Lithium-ion	Lithium-metal, solid-state	Mainly sodium-ion
Storage mode	Intercalation between layers	Metallic lithium plating (no host)	Storage in wide interlayers and closed pores
Specific capacity (mAh/g)	372 (theoretical)	3,860 (theoretical, about 10.4x graphite)	About 300 (typical, sodium)
Main challenge	Capacity ceiling, concentrated supply chain	Dendrites, low Coulombic efficiency	Sodium-ion-specific material, early mass production
Target application	General-purpose EV	Premium EV	Entry-level EV and ESS

What this table says: lithium metal promises about 10 times more capacity than graphite but carries safety challenges, while hard carbon has lower capacity than graphite but reduces raw-material burden by using a different chemistry, sodium. The two materials are less competitors for the same slot than parallel tracks aimed at different markets.

The readiness of the hard carbon track in Korea can be gauged from the case of Aekyung Chemical. Putting the reports together, the flow is as follows.

Timing	Details
2024	Developed a biomass-based hard carbon anode material for sodium-ion batteries
2025	Unveiled a product with improved performance
December 2025	Decided to expand the production line at its Jeonju plant to handle large-scale customer pilot tests; reported as Korea’s first mass-production facility for sodium-ion battery anode material
March 2026	Building a 1,300-ton-per-year facility at the Jeonju plant, with a future target of 20,000 tons per year; at the stage of handling customer pilot tests

What this table says: the plan to go from 1,300 tons to 20,000 tons is an expansion of about 15 times, and as of March 2026 the business was still at the customer pilot stage.

Here we add one interpretation not in the original post. The items specified in China’s 2023 export-control announcement are artificial graphite materials and natural flake graphite products. Hard carbon made from biomass is not graphite, so by the wording of the announcement it sits apart from that list. In this respect, the hard carbon track can be read not merely as a material swap but as an option that “moves the supply chain outside the regulated items”. However, whether it falls under the list by actual customs classification (HS code) needs separate confirmation.

Patent perspective: rights hinge on “combinations and parameters” rather than the material itself

Suppressing lithium-metal dendrites is an area where filings cluster around interfacial engineering (design of protective layers on the anode surface and solid-electrolyte interphase layers). Whether it is combined with solid-state batteries could become the watershed for commercialization patent strategy. However, since this article did not check the bibliographic data of individual lithium-metal patents, no specific numbers are given.

A case on the hard carbon side whose bibliographic data was verified is Toyota Motor Corp’s U.S. granted patent US11735715B2 (“Anode material for sodium ion battery, and sodium ion battery”). Its priority date is November 7, 2019, filing date October 21, 2020 and grant date August 22, 2023; according to Google Patents its legal status is Active and its anticipated expiration date is April 29, 2041.

Restating the gist of claim 1, it is an anode material that contains amorphous glassy carbon with a BET specific surface area of 32 to 1,050 m²/g together with a sodium complex hydride solid electrolyte (NaMH compound), a solid solution containing NaCB₉H₁₀ and NaCB₁₁H₁₂, in a weight ratio of 40:60 to 70:30. The specification explains that this combination improves initial charge-discharge efficiency.

This case shows two features of the rights structure. First, the right is attached not to the carbon material itself but to a combination of “a physical-property parameter such as specific surface area + a specific solid electrolyte + a mixing ratio”. Second, as a result, the scope of rights becomes narrow and clear. A hard carbon anode in an ordinary sodium-ion cell using a liquid electrolyte lacks the solid-electrolyte element, so the risk of literal infringement of this claim is likely to be low.

The design-around scenario and counterargument are as follows.

• Design-around: switching the solid electrolyte to a family other than NaMH, or designing the carbon’s BET specific surface area or the mixing ratio outside the claimed ranges, could take it outside the literal scope of rights.
• Counterargument: values in parameter claims can differ depending on the measurement method, so even if one’s own measured value is outside the range, it could fall inside the range under the other party’s measurement conditions. The possibility of a doctrine-of-equivalents argument (the legal principle that treats an element performing substantially the same role as infringing) must also be weighed separately.

Hard carbon manufacturing-process patents may diverge depending on the feedstock (biomass vs. petroleum-based). Hard carbon patents filed by Aekyung Chemical could not be confirmed from published patent information this time and remain a tracking point.

Limitations and outlook: the two tracks move at different speeds

Aekyung Chemical’s plan to expand from 1,300 tons to 20,000 tons is at the announcement stage, and the actual utilization rate and whether quality stabilizes require further confirmation. For lithium metal, too, the dendrite and Coulombic-efficiency problems are tied to the commercialization schedule of solid-state electrolytes, so the point at which it actually replaces graphite is likely to come later than for the hard carbon track.

The counter-scenario to the optimistic outlook comes from the graphite side. If graphite prices stabilize more than expected and graphite supply sources outside China increase, the cost rationale for leaving graphite weakens and the pace of the shift away from graphite could slow. In particular, since hard carbon has lower capacity than graphite, once the raw-material-risk rationale weakens, the case for adoption narrows to price alone.

The strategic alternative is to see this as “diversification” rather than “replacement”. In the short term, reduce risk by diversifying graphite suppliers; qualify sodium-ion and hard carbon as a second supply chain in entry-level and ESS lineups; and manage lithium metal as a long-term option tied to the solid-state roadmap.

Practical action: materials and IP staff should obtain product properties (such as BET specific surface area) and measurement conditions from candidate hard carbon suppliers, and first build an FTO checklist that compares them against the numerical ranges of parameter-type patent claims.

Items requiring verification

• Base year and source of the figure that graphite holds more than 90% of the anode material market
• Confirmation by HS code that biomass-based hard carbon does not fall under China’s graphite export-control items
• Start of operation of the 1,300-ton facility at Aekyung Chemical’s Jeonju plant and the schedule for expansion to 20,000 tons
• Status of Aekyung Chemical’s domestic and overseas patent filings related to hard carbon
• Key granted patents and rights holders in the field of lithium-metal interfacial protective layers

Sources

1. China SCIO, “China announces export control on certain graphite materials, products”, 2023-10-20
2. IEA Policies, Announcement on the optimisation and adjustment of temporary export control measures for graphite items
3. Qian et al., “High rate and stable cycling of lithium metal anode”, Nature Communications, 2015
4. Tang et al., “Revealing the closed pore formation of waste wood-derived hard carbon for advanced sodium-ion battery”, Nature Communications, 2023
5. Seoul Economic Daily, “Aekyung Chemical expands hard carbon anode material at Jeonju plant”, 2025-12-04
6. Money Today, “Aekyung Chemical expands secondary battery materials business”, 2026-03-10
7. Google Patents, US11735715B2