Fluorine chemistry reshapes the future of lithium batteries: from trifluoroethylene to "one shot" regeneration

A fluorine-containing gas once used in industrial synthesis is becoming the key to breaking the curse of lithium battery life

In 2021, Chen Mao's research group at Fudan University used chlorotrifluoroethylene gas as raw material to design a main chain fluorinated alternating copolymer. This material is non-flammable, non-crystalline and chemically stable, and for the first time achieves the compatibility of efficient lithium ion transmission at room temperature and 5.3V high-voltage stability.

Four years later, the school's team of Peng Huisheng and Gao Yue published a disruptive result in Nature - by injecting the fluorine-containing organic lithium salt "lithium trifluoromethanesulfinate", the cycle life of the lithium battery exceeded 11,818 times (capacity retention rate 96%) , extending the life by more than 10 times.

These two breakthroughs point to one core logic: fluorine chemistry is rewriting the underlying rules of lithium batteries.

01 The “Breakthrough” Gene of Fluorine Chemistry: From Chlorotrifluoroethylene to Polymer Electrolytes

The bottleneck of lithium batteries has long existed in the contradiction between interface stability and lithium loss . Traditional fluoropolymers are difficult to meet the needs of solid-state batteries because they are easy to crystallize and have poor ability to dissolve lithium salts.

The synthesis route of chlorotrifluoroethylene provided new ideas:

Precisely control the molecular structure : Using gaseous chlorotrifluoroethylene as a monomer, the main chain fluorinated alternating copolymer is synthesized under mild conditions, breaking through the limitations of high temperature and high pressure synthesis;

Hexacyclic stabilization mechanism : The polymer and lithium ions form a ring structure, which produces a weak solvation effect and inhibits the growth of lithium dendrites;

High-voltage compatibility : Remains stable in an ultra-wide electrochemical window of 5.3V, paving the way for high-energy-density battery design.

This achievement reveals the potential of fluorinated polymers as electrolyte substrates, but they are still unable to address the fundamental contradiction of "lithium loss".

At the beginning of 2025, the team of Peng Huisheng and Gao Yue proposed the "external lithium supply" technology , pushing the application of fluorine chemistry to a new dimension. Its core is a fluorine-containing molecule called lithium trifluoromethanesulfinate (CF₃SO₂Li) , which solves the lithium loss dilemma through three major properties:

Precise decomposition : Irreversible oxidation within the 2.8-4.3V charging voltage window, releases lithium ions and decomposes into gases such as SO₂ and CHF₃, achieving "zero residue" through the exhaust system ;

Industrial universality : It is soluble in conventional electrolytes, compatible with graphite, silicon-carbon negative electrodes and various positive electrode materials, and the synthesis cost is less than 10% of the total battery cost;

AI-enabled design : 3 million virtual molecular libraries are screened through unsupervised machine learning, and the optimal solution is locked by comprehensively considering parameters such as electrochemical activity and solubility.

The four-step rebirth technique of "injection" technology :

Solution preparation : Dissolve CF₃SO₂Li in the electrolyte at a concentration of 12.5%;

Injection : Inject into aged batteries through the reserved air holes or conduits of the batteries;

Activation : During charging, lithium salt decomposes at the anode and lithium ions are embedded in the negative electrode;

Purification : After the decomposition gas is discharged and sealed, the battery returns to its initial performance.

This technology reduces the cost of energy storage batteries to 0.03 yuan/Wh (a 70% reduction) and makes "lithium-free positive electrode" possible - materials such as chromium oxide (CrO) enable energy density to reach 1192 Wh/kg, which is three times that of lithium iron phosphate.

Innovations in fluorinated materials are surging from laboratories to the industrial front:

Lithium replenishment technology + large battery cells : 688Ah energy storage cells combined with external lithium replenishment enable the 20-foot container system capacity to reach 6.9MWh, with a cycle life exceeding 15,000 times, supporting 20 years of maintenance-free operation of offshore wind power platforms;

Recycling of retired batteries : By 2030, China’s retired energy storage batteries are expected to reach 2 million tons. Lithium replenishment technology can extend their lifespan by 5-10 times and reduce solid waste by 70%;

Manufacturing process innovation : The existing production line only needs to add a liquid injection process to be compatible with the new process, and well-known domestic companies have promoted cooperation.

Despite its promising prospects, the technology still needs to overcome three hurdles:

Long-term safety : The cumulative effect of multiple injections on the SEI membrane needs to be verified;

Standardized adaptation : The injection interface of square shell/cylindrical batteries needs to be redesigned;

Economic balance : Repair service costs need to compete with battery replacement costs.

In response to this, the team is developing "pre-embedded" molecules - which are injected into the battery when it leaves the factory and activated to release lithium ions when the capacity decays, achieving "zero intervention" repair.

From the high-voltage stable interface constructed on the trifluoroethylene substrate to the fluorine-containing "life-extending molecules" designed by AI, the two leaps of fluorine chemistry in the field of lithium batteries reveal the same logic:

The precise control capabilities of fluorine-containing materials are solving the ultimate contradiction in energy storage - humans no longer have to choose between increasing density and extending lifespan.

As Peng Huisheng's team envisions: "In the future, we will repair batteries through 'injections' to make the industrial ecology intelligent and environmentally friendly." When the 688Ah battery cell meets the fluorine-containing lithium supplement, a revolution that rewrites the underlying logic of energy storage has begun.