What’s the Story: The Lesson Left by an Invalidated Patent
In the fight over the foundational patents for LFP (lithium iron phosphate) batteries, what matters more than “there was a patent” is “how the patent collapsed in China.” A Chinese patent on a method for synthesizing carbon-coated LFP held by Hydro-Québec and others (CN100421289C) was granted on September 24, 2008, but the China Battery Industry Association filed an invalidation request in August 2010, and on May 28, 2011, all 111 amended claims were reportedly declared invalid. This article sets out what the grounds for invalidation were, and why this case is worth rereading now that the foundational patents have all expired.
Starting with the industry context: while Korea’s three battery makers traded tension over prismatic-cell patents in March 2026, China has reportedly been organizing a large, government-led patent pool bundling CATL, BYD, and others to respond systematically to overseas IP disputes. This aggressive patent strategy did not appear out of nowhere. Twenty years ago, Chinese companies were on the receiving end of licensing demands for the LFP foundational patents, and they have the experience of escaping that burden through the legal tool of patent invalidation.
This is where the tension lies. However strong a foundational patent may look, if it collapses in a given country on procedural defects, that country’s entire industrial landscape can shift. This article answers three questions: what did the LFP foundational patents claim, why was the Chinese patent invalidated, and what should today’s planning and IP professionals take away from this case?
Basic Principle: A Wide Road with No Lane for Electrons
The LFP foundational patents split into two branches. One is the University of Texas patent claiming the olivine-structured (a crystal structure in which atoms are arranged in a specific lattice) LiMPO₄ cathode material itself; the other is a family of patents from Hydro-Québec, the Université de Montréal, and CNRS claiming technology that raises electrical conductivity by coating the material’s surface with carbon. According to reports, the LFP material was discovered at the University of Texas at Austin in 1995.
Source: reconstructed by the editorial team from claim 1 of CN100421289C
By analogy, LFP is like a wide, sturdy road. Its raw materials are cheap and its structure is stable, so accidents (thermal runaway) rarely happen. The problem was that electrons had a hard time traveling along this road — in other words, its electronic conductivity was low. Carbon coating works like laying a dedicated electron lane on the road surface. Wrapping each particle in a thin carbon film creates paths for electrons to flow between particles, and only then does LFP become a practical cathode material.
CN100421289C, which was invalidated in China, belongs to this carbon-coating branch, but it claims a synthesis method rather than the material itself. Restated, claim 1 reads as follows.
- It is a method for synthesizing a carbon-bonded C-LixM1-yM’y(XO₄)n compound
- A precursor mixture of transition-metal (M, M’) sources, a lithium source, an X source, and a carbon source is equilibrated under a gaseous atmosphere
- Temperature, gas composition, and precursor ratios are controlled to bring the transition metal’s oxidation state to the desired level
- The carbon source is pyrolyzed to obtain a conductivity above 10⁻⁸ S/cm in a powder sample compressed at 3750 kg/cm²
Comparison: Three Representative Patents, Three Fates
The table below cross-checks the two branches of foundational patents mentioned in the original article, plus the Chinese patent, against Google Patents bibliographic data. Even among “foundational patents,” the claimed subject matter and expiry dates differ.
| Item | US5910382A | US6855273B2 | CN100421289C |
|---|---|---|---|
| Claimed subject matter | LiMPO₄ cathode material (M: first-row transition metal) | Electrode material with conductive carbon deposited homogeneously on its surface | Method for synthesizing size-controlled carbon-coated redox materials |
| Original applicant | University of Texas System | Université de Montréal, Acep Inc, CNRS | CNRS, Université de Montréal, Hydro-Québec |
| Inventors (partial) | John B. Goodenough, Akshaya K. Padhi, and 2 others | Nathalie Ravet, Michel Armand, and 4 others | M. Armand, N. Ravet, and 2 others |
| Priority date | 1996-04-23 | 1999-04-30 | 2000-09-26 |
| Grant date | 1999-06-08 | 2005-02-15 | 2008-09-24 |
| Current status | Expired (2017-04-21) | Expired (2020-05-04) | Ceased (2021-09-21), with a history of invalidation in China |
Source: compiled by the editorial team from Google Patents bibliographic data (US5910382A, US6855273B2, CN100421289C)
What this table says: The material patent (US5910382A) expired in the US in 2017 and the coated-material patent (US6855273B2) in 2020, while the Chinese synthesis-method patent was already caught up in an invalidation fight before it expired. The expiry that the original article lumped together as “sequentially in 2021–2022” actually differs by more than four years from patent to patent.
Two points in the original account need correcting. First, the inventor list of US5910382A names Goodenough, Padhi, Nanjundaswamy, and Masquelier; Dr. Manthiram, introduced in the original as a co-discoverer, is not listed as an inventor on this patent. Second, the patent’s priority date is April 23, 1996; 1995 is the year the material was reportedly discovered. Interestingly, Google Patents lists Hydro-Québec as the current assignee of US5910382A, showing that the two branches of patents ultimately converged in a single camp.
Patent Perspective: The Grounds for Invalidation Were Not Prior Art
The course of enforcement: The Hydro-Québec camp invested heavily in protecting its patents. The lawsuit the University of Texas and Hydro-Québec brought against Japan’s NTT in Texas ended on October 6, 2008, in a $30 million settlement. According to NTT’s announcement, however, the cause of action was misappropriation of trade secrets concerning lithium rechargeable-battery technology, and NTT settled while denying the allegations, to avoid litigation costs and the uncertainty of a jury trial. Then in July 2011, Hydro-Québec, the Université de Montréal, CNRS, and Süd-Chemie set up a sublicensing entity called LiFePO4+C Licensing AG, and four companies including Taiwan’s Advanced Lithium Electrochemistry (Aleees) were announced as the first sublicensees.
The Chinese invalidation case: According to Chinese reports, the patentee side demanded from Chinese companies a $10 million entry fee and a royalty of $2,500 per ton of LFP. The China Battery Industry Association filed an invalidation request in August 2010, and on May 28, 2011, all 111 amended claims were declared invalid. The grounds were that the amendments went beyond the scope of the original application (addition of new matter) and that the claims were not supported by the specification. The patentee side appealed, and a hearing was held at the Beijing No. 1 Intermediate People’s Court on April 9, 2012, but reportedly no judgment was issued that day.
Source: reconstructed by the editorial team from the claims of CN100421289C and reports on the Chinese invalidation case
Insight: The lesson of this case lies not in the “technology” but in the “amendment history.” The grounds for invalidation were not the discovery of earlier prior art, but a procedural problem: in revising the claims during examination, the patentee went beyond the scope of the original specification. In other words, even if an invention is novel and inventive, weak specification drafting and amendment management can put the entire scope of rights at risk. The fact that the amended version, which cut 125 claims down to 111, was invalidated wholesale also shows that simply increasing the number of claims does not secure the stability of rights. The same logic could apply in reverse to Korean companies filing in China today.
Avoidance points: The scope of rights of this method patent requires every one of several elements — equilibration under a gaseous atmosphere, oxidation-state control, pyrolysis of a carbon source, and conductivity under a specified compression condition — to be met for literal infringement (the all-elements rule). So from the standpoint of Chinese companies at the time, design-arounds that changed the carbon source or the process sequence were, in theory, candidates for review.
Design-around scenario (rebuttal): That said, it is hard to consider a process change alone to be safe. If the resulting product, carbon-coated LFP, is the same, the patentee could potentially contest on the basis of material claims (the US6855273B2 family) or the doctrine of equivalents, and while method patents are hard to prove on the factory floor, they can become a means of attack through presumption rules applied to imported products. In the end, the path Chinese companies took was not individual design-arounds but an invalidation attack through an industry association — a case showing a structure in which an invalidation attack can be more cost-effective than a design-around.
Limitations and Outlook
The expiry of the foundational patents does not mean LFP patent competition is over. As CATL has reportedly filed a string of utility-model infringement suits even against domestic startups, the center of gravity has shifted from “who holds the foundational technology” to “who has built up a tighter web of detailed process and composition patents.” The fact that an industry with the experience of invalidating a foundational patent has now become the side most aggressively asserting its rights is the reason this case deserves a second reading.
The optimistic view is that, with the foundational patents all expired, LFP has become public technology anyone can use without royalty burdens. There is an opposing scenario as well. The space left by the foundational patents is being filled by thousands of improvement patents and utility models on particle design, doping, calcination processes, and cell structure, so the actual FTO (freedom-to-operate) burden at the product level may well have grown.
A strategic alternative is to use “expired foundational patents” as defensive assets. The specification of an expired foundational patent serves as evidence of technology anyone may freely practice, so if a later improvement patent overlaps with that scope, it can become the starting point for a prior-art defense or an invalidity argument. As the Chinese invalidation case shows, checking the amendment history of an opponent’s patent belongs to the same set of defensive tools.
Practical action: Professionals planning LFP cathode materials or cells should obtain the prosecution history (amendments and responses) of competitors’ key LFP patents and first flag any claims whose scope was broadened by amendment relative to the original specification.
Items requiring verification
- Whether the original article’s “filed in China in 2003” refers to CN100421289C’s Chinese national-phase entry date (the filing date on Google Patents is 2001-09-21)
- The final outcome of the administrative litigation over the CN100421289C invalidation decision after the April 9, 2012 hearing
- The primary source for the original article’s statement that Aleees paid 10% of its LFP revenue in patent royalties
- Whether, and for how long, Chinese companies such as CATL and BYD actually paid royalties
- Primary reports on the March 2026 government-led Chinese patent pool and on CATL’s utility-model suits
- Expiry dates of the overseas family members (Europe, Japan, etc.) of US5910382A and US6855273B2
Sources
- Google Patents, US5910382A – Cathode materials for secondary (rechargeable) lithium batteries
- Google Patents, US6855273B2 – Electrode materials with high surface conductivity
- Google Patents, CN100421289C – Method for synthesizing size-controlled carbon-coated redox materials
- NTT press release, Notice regarding Settlement of a Lawsuit filed in Texas, U.S.A. (2008-10-06)
- Green Car Congress, Hydro-Québec, Université de Montréal, CNRS and Süd-Chemie create entity for sublicensing of lithium iron phosphate battery materials (2011-07-04)
- China Energy Storage Network (escn.com.cn), “Patent invalidation case goes to court: a life-or-death test for the LFP battery industry” (2012)