Brief Overview of the Physical Microwave Repair Process for Spent Cathode Sheets

Henan Jufeng Technology Co., Ltd. has formed a powerful partnership with the Institute of Process Engineering, Chinese Academy of Sciences, and after ten years of dedicated research, they have successfully developed a physical dry-process repair and regeneration technology for lithium‑battery cathode sheets. This technology abandons traditional, low‑end crushing processes and instead addresses the industry’s long‑standing pain points—such as low recovery rates, structural damage, difficulty in direct reuse, and poor economic viability—through repair and regeneration. The technology has now reached its 6th generation, with its core advantages lying in its short process flow, use of dry‑phase physical regeneration, zero pollution, low energy consumption, and the ability to perfectly preserve the crystal structure of cathode materials. During the high‑temperature stage, the equipment is manufactured using Hastelloy C22, C200, C276, and Monel alloys—materials that are highly resistant to hydrofluoric acid corrosion. In the low‑temperature stage, Hastelloy thermal spraying, ceramic spraying, and Teflon spraying techniques are employed, effectively preventing corrosion by hydrofluoric acid while also safeguarding against trace metal impurities that may contaminate the repaired and regenerated materials when the cathode material comes into contact with the metallic substrate. As a result, this technology delivers high‑purity, high‑performance regeneration outcomes. To date, all technological routes have achieved industrial production capacity exceeding 10,000 tons.

The fourth-generation technology developed employs a full-process production method that combines “pyrolytic exfoliation + microwave repair and regeneration.” This approach enables the physical dry‑recovery of waste cathode sheets through a four‑step process: “thermal cracking + flexible exfoliation + microwave repair + crushing and grading.” The process is characterized by its short workflow, zero pollution, low energy consumption, and superior performance, making it a new, integrated pathway. Its core technology lies in controlling the oxygen content of the cathode sheets to below 10 ppm under a protective atmosphere, followed by calcination of the material at temperatures ranging from 150°C to 600°C. This treatment promotes the volatilization and thermal decomposition of binders, allowing for the flexible separation of the cathode material from the aluminum foil without damaging the cathode material itself. The exfoliated cathode material then undergoes microwave repair to restore the crystal structure that has been altered by minor defects; after microwave repair, the material is crushed and graded, ultimately yielding repaired and regenerated cathode material with battery‑grade performance. This process perfectly preserves the olivine structure and electrochemical properties of lithium iron phosphate, while leveraging physical repair techniques to restore and enhance its performance—techniques that have already been widely adopted across the industry.

Through the concerted efforts of Jufeng and the research team led by Dr. Kang Fei, working alongside the team of Academician Cao Hongbin at the Institute of Process Engineering, Chinese Academy of Sciences, the fifth-generation cathode plasma regeneration technology has been successfully developed after more than two years of research and development. This technology employs a full-process production method that combines “low‑temperature plasma + microwave thermal repair and regeneration,” achieving physical dry‑process regeneration of waste cathode sheets through four sequential steps: “low‑temperature plasma decomposition + flexible delamination + microwave repair + crushing and grading.” Currently, this technology has been implemented in multiple companies within the industry.

In October 2025, Professor Jufeng and the Institute of Process Engineering, Chinese Academy of Sciences, once again developed the 6th-generation subcritical hydrolysis regeneration technology (also known as superheated steam regeneration technology). This technology employs a “subcritical water decomposition (superheated steam decomposition) + drying + flexible peeling + microwave repair + crushing and classification” process to treat waste cathode sheets in five steps, achieving physical dry‑state regeneration. At present, this technology has already reached small‑scale production capacity.

The positive electrode physical regeneration technology developed by Jufeng Company is an economically viable, green, and low‑carbon approach. The company has accumulated profound expertise and extensive engineering experience in this field, and all of the aforementioned regeneration technology pathways are now equipped with industrial production lines capable of handling annual capacities of 10,000 tons per line.

Brief Overview of the Microwave Physical Repair Process for Positive Electrode Sheets

Step 1: Anaerobic Pyrolysis: Remove organic impurities from the positive electrode sheet, primarily the binder (such as PVDF).

Principle: Under anaerobic conditions with an oxygen content below 10 ppm, the waste lithium iron phosphate cathode sheets are subjected to pyrolysis (at temperatures ranging from 200–600°C), causing the organic binder PVDF to decompose into small molecules such as HF, CO₂, and alkanes. This process breaks the bond between the powder and the foil while simultaneously retaining approximately 3 wt% of conductive carbon on the particle surfaces in situ. The pyrolysis equipment is fabricated from Hastelloy C22, C200, and C276 materials, which are resistant to hydrofluoric acid corrosion, effectively preventing damage caused by HF.

Function:

1. “Loosening Soil” Effect: The binder firmly adheres the active material (LFP) and conductive agent to the aluminum foil. After thermal decomposition, the bonding strength between the cathode material and the aluminum foil is significantly reduced, paving the way for flexible powder detachment.

2. Purification: It simultaneously thermally decomposes the solid electrolyte interphase (SEI) film and organic components, purifying the lithium iron phosphate material while preventing the oxidation of Fe²⁺ to Fe³⁺ and preserving the integrity of the LFP crystal lattice.

Step 2: Flexible Powder Removal: Completely and efficiently strip the pyrolyzed lithium iron phosphate material from the aluminum foil.

Principle: After pyrolysis, the bond between the material and the aluminum foil becomes extremely weak. By employing “gentle” methods such as high‑velocity air jets or soft kneading, the LiFePO₄ powder layer can be completely peeled off in a single sheet, achieving a powder–foil separation rate of over 99%. The aluminum content is less than 0.03%, with zero damage to the powder particles and intact, well‑defined particle morphology. This flexible powder‑removal equipment utilizes tungsten carbide coatings and ceramic spraying to prevent metal contamination of the materials.

Function:

1. Efficient Separation: Achieve clean separation of aluminum foil and cathode powder, yielding aluminum foil that is clean, intact, and highly valuable.

2. Low Damage: “Flexibility” is designed to peel rather than crush, causing minimal damage to the crystal structure of lithium iron phosphate and preventing material defects and iron contamination caused by excessive mechanical grinding.

Step 3: Microwave Physical Repair : Repair the structural defects present in lithium iron phosphate and restore its electrochemical performance.

Principle: Microwaves can effectively remove residual carbon coatings from the material’s surface, inducing graphitization of pyrolytic carbon and thereby increasing the material’s tap density (or, in the presence of a carbon source, forming new, superior conductive carbon coatings).

Function:

1. Selective Heating: Lithium iron phosphate materials exhibit excellent microwave absorption properties. In a 2.45 GHz microwave field, the polar molecules and carbon atoms within the material undergo rapid friction and reorientation, instantly generating high temperatures throughout the material and achieving “volume heating.” This heating method is far more efficient than traditional external conduction heating and ensures uniform heating.

2. Defect Repair: Under microwave rapid heating conditions (in a specific atmosphere), the amorphous layer and microcracks on the particle surface undergo recrystallization at high temperatures, thereby repairing the crystal structure. The unique “volume heating” characteristic of microwaves enables lattice defects to reach extremely high temperatures in an instant, facilitating the filling of Li⁺ vacancies and the reduction of Fe³⁺, which in turn allows for the rapid reconstruction of the crystal structure.

Step 4: Crushing of Repair Materials: Crushing is used to achieve a suitable particle size distribution for the material.

Principle: Through physical methods such as crushing, grinding, and sieving, the recycled lithium iron phosphate is finely pulverized to a D50 particle size of approximately 1–2 µm. A suitable particle size ensures uniform dispersion of the active material with the conductive agent and binder during electrode sheet fabrication, thereby delivering consistent performance. Ceramic spraying and Teflon spraying are employed to prevent contamination by trace metal impurities.

Function:

1. Enhance Material Consistency: Obtain powders with uniform particle size to ensure stable quality in battery regeneration products, thereby improving their charge–discharge capacity and cycle life.

2. Deep Purification: After gentle ball milling → d50 ≈ 2 μm → demagnetization → sieving, the material can be directly coated to prepare recycled cathode sheets, or blended with 30–60% virgin material for use.

Characteristics of Pyrolysis Microwave Physical Regeneration and Repair

1. Environmentally friendly, green and low‑carbon

· No strong acids or strong bases: The entire process employs physical methods and a short‑process thermal approach, avoiding the large volumes of high‑salinity wastewater, waste acid, and waste residue generated by hydrometallurgy, resulting in a minimal environmental burden.

· Low energy consumption: Microwave heating boasts extremely high efficiency and rapid temperature rise—on the order of seconds or minutes—far shorter than the several hours required for conventional muffle furnaces, significantly reducing energy usage.

· Controllable exhaust gases: The organic exhaust gases generated during pyrolysis can be collected centrally and routed to waste gas treatment systems such as a thermal oxidizer (TO), enabling compliance with emission standards and facilitating easy management.

2. Short process flow and high efficiency

· The four-step process is closely integrated, seamlessly transitioning from waste electrode sheets to recycled materials. The process is simple and easy to implement for continuous and automated production, resulting in high production efficiency.

3. Recycled materials exhibit excellent performance.

· Low‑damage repair: Both “soft powder removal” and “microwave repair” are designed to minimize secondary damage to the particles. The crystalline structure of the repaired material remains intact, and its tapped density is high.

· Excellent electrochemical performance: The regenerated lithium iron phosphate material can achieve capacity per gram, cycle life, and rate capability that are comparable to, or even match, those of new materials, making it suitable for direct use in the production of new batteries.

4. High resource recovery rate and good economic performance.

· Complete recovery of valuable components: Not only does it efficiently recover high‑value lithium iron phosphate powder, but it also yields clean, intact aluminum foil that can be sold directly as a metal raw material, thereby enhancing overall economic benefits.

· Complete retention of lithium, iron, and phosphorus: The physical method does not involve chemical leaching of these elements, so nearly all of the lithium, iron, and phosphorus remain in the final product with no loss.

5. Clear Advantages in Core Technologies

· The uniqueness of microwave repair: It achieves “in-situ repair” of materials and enhances their specific capacity—rather than dismantling, pulverizing, and then synthesizing via wet chemistry—making it true “regeneration” rather than “recycling.” Its rapid, volumetric heating characteristics are unmatched by conventional heat treatment.

High Efficiency and Short Processes: The process flow is concise, eliminating the complex steps involved in wet processing, with a material recovery rate exceeding 98%.

6. Low Costs and Cost Reduction with Efficiency Gains: By eliminating the need for expensive chemical reagents, the cost of repairing and regenerating per ton is only approximately RMB 1,500, and the cost of repair materials can be as low as 100% of that of new materials, enabling downstream cell manufacturers to reduce costs by more than 25%.

7. High Environmental Protection and Low Energy Consumption: The entire process generates no wastewater or waste residue, thereby preventing secondary pollution, and its energy consumption is far lower than that of wet processes.

8. Excellent performance and stable structure: The microwave repair material retains its original crystal structure and increases the tap density. The discharge specific capacity after repair can reach over 98.5% of that of new material, while exhibiting outstanding cycling performance.

9. Structural Integrity and Performance Comparable to New Material: During the delamination process, the particles remain undamaged and exhibit no lattice distortion; the peak half‑width is comparable to that of commercially available products. The reversible specific capacity at a 0.1 C rate is 155.7 mAh/g, while at a 1 C rate it is 144.6 mAh/g. The initial Coulombic efficiency at a 0.1 C rate is 97.5%, and after 150 cycles at a 1 C rate, the capacity retention rate is 96.4%, with a difference of less than 1.3% compared to the new material.

Positive Electrode Repair and Regeneration Test Report

Images of equipment and related materials

Positive Electrode Pyrolysis Off-Gas Treatment Equipment

Positive Electrode Regeneration Crushing and Mixing Equipment

Positive Electrode Oxygen-Free Pyrolysis Equipment