From Old Batteries to New Fertilizers: The Closed-Loop Revolution in LFP Battery Recycling

I. Why Choose LFP Batteries? The Unique Advantage of Recycling Phosphate Fertilizers Among various lithium-ion batteries, lithium iron phosphate (LFP) batteries have lower traditional recycling economic value due to their lack of expensive metals like cobalt and nickel. However, the chemical essence of their cathode material, LiFePO₄—a compound containing lithium, iron, phosphorus, and oxygen—offers a unique perspective for resource utilization. Phosphorus, as one of the three essential elements for plant growth, is a strategic resource for global food security. Traditional phosphate fertilizer production heavily relies on non-renewable phosphate rock and involves high energy consumption and pollution. Recovering phosphorus from spent LFP batteries is equivalent to opening a new, renewable phosphorus resource library in the urban "mine," effectively alleviating dependence on natural phosphate rock and reducing the environmental footprint of mining. II. Technical Core: How to "Release" Phosphorus Nutrients from Batteries? The technical core of this process is converting phosphorus in LFP cathode materials into a form usable by plants. Latest research reveals several efficient and green technological pathways. 1. Selective Extraction and Transformation Researchers have developed an in-situ advanced oxidative metallurgy technique based on the Fenton reaction. This technology uses highly oxidative hydroxyl radicals (•OH) to selectively oxidize ferrous iron (Fe²⁺) in LiFePO₄ and promote the complete release of lithium ions (Li⁺), while the phosphate group (PO₄³⁻) framework within the olivine crystal structure is preserved, forming amorphous or crystalline iron phosphate (FePO₄). The key to this process is precise reaction control to retain phosphorus in the solid product, preventing its loss or pollution by entering the solution. Subsequently, these phosphorus-rich intermediates can be further processed, for example, combined with potassium and nitrogen sources to prepare slow-release PK or compound fertilizers with different formulations. 2. Direct Functionalization and Material Design Besides serving as a phosphorus source, recycled lithium iron phosphate (LFP) materials, due to their unique structure and chemical properties, can be directly designed into fertilizers or soil conditioners with special functions. For example, micronizing blocky LFP materials using technologies such as laser crushing can increase their specific surface area. The iron and phosphorus species on their surface can form active sites; studies have shown that these substances can not only act as catalysts for water electrolysis but also regulate the release rate of nutrients in the soil or engage in beneficial interactions with soil microorganisms. This "material-level" recycling upgrade endows waste batteries with functional attributes far exceeding their elemental value. III. Product Advantages: How Do Slow-Release Fertilizers Benefit Agriculture? Phosphate fertilizer products derived from LFP are not simple substitutes for traditional fertilizers; they may possess a range of enhanced properties: · Slow-Release Features: LFP itself or derived iron phosphate compounds have low solubility in water, which aligns perfectly with the core requirement of slow-release fertilizers. Phosphorus can be slowly released through the action of soil moisture, microbial activity, or weak acids secreted by roots, avoiding the issue of rapid fixation or loss after a single application and significantly improving phosphorus use efficiency. · Nutrient Synergy: In addition to phosphorus, the products typically contain iron. Iron is a mesonutrient required for plant chlorophyll synthesis and is beneficial for correcting iron-deficiency chlorosis. Lithium, in trace amounts, is also considered by some studies to potentially promote growth in certain crops. · Environmental Friendliness: This process transforms toxic waste (spent batteries) into an environmentally friendly product (fertilizer). Compared to the acidic wastewater generated by traditional hydrometallurgical phosphorus recovery, the new conversion routes lean toward greener chemical processes with a lower environmental burden.

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