Recycling Characteristics Of Lithium Iron Phosphate Batteries

Rapid growth and large scrap
Since the development of the electric vehicle industry, China has been the world's largest consumer market for lithium iron phosphate. In particular, from 2012 to 2013, it was growing at a rate of nearly 200%, and the sales of lithium iron phosphate in China in 2013 were about 5797 tons, accounting for more than 50% of the global sales.
In 2014, 75% of lithium iron phosphate cathode materials were sold to China, and the theoretical life of lithium iron phosphate batteries is 7~8 years (calculated in 7 years), and it is expected that about 9,400 tons of lithium iron phosphate will be scrapped by 2021.

The harm is significant
The chemical substances contained in lithium iron phosphate batteries such as LiPF6, organic carbonate, and copper are all in the national hazardous waste list. LiPF6 is highly corrosive and easy to decompose in water to produce HF. Organic solvents and their decomposition and hydrolysis products will cause serious pollution to the atmosphere, water and soil, and cause harm to the ecosystem. Heavy metals such as copper accumulate in the environment and eventually harm humans themselves through the biological chain; Once phosphorus enters lakes and other water bodies, it is very easy to cause eutrophication of water bodies. It can be seen that if the discarded lithium iron phosphate batteries are not recycled, it will be extremely harmful to the environment and human health.

Recycling technology is immature
Existing data show that the recycling of waste lithium iron phosphate batteries is divided into two types: one is to recycle metal, and the other is to recycle lithium iron phosphate cathode materials.
(1) Wet recovery of lithium and iron
This type of process is mainly based on lithium recovery, because lithium iron phosphate does not contain precious metals, so the recovery process of lithium cobalt oxide is modified. First, the lithium iron phosphate battery is disassembled to obtain the cathode material, and the powder is crushed and screened. After that, the alkali solution is added to the powder to dissolve aluminum and aluminum oxides, and filter the filter slag containing lithium and iron. leaching the filter slag with a mixed solution of sulfuric acid and hydrogen peroxide (reducing agent) to obtain the leachate; Alkali is added to precipitate iron hydroxide and filtered to obtain filtrate; Iron oxide can be obtained by burning iron hydroxide; Finally, the pH value of the leachate (5.0 ~ 8.0) is adjusted, the leachate is filtered to obtain the filtrate, and the solid sodium carbonate is concentrated and crystallized to obtain lithium carbonate.
(2) Regenerated lithium iron phosphate
A single recovery of an element makes the economic benefits of recycling lithium iron phosphate that do not contain precious metals relatively low. Therefore, the solid-phase method is mainly used to regenerate lithium iron phosphate to treat waste lithium iron phosphate batteries, which has high recycling benefits and high comprehensive utilization of resources.
First, the lithium iron phosphate battery is disassembled to obtain the cathode material, and the powder is crushed and screened. After that, heat treatment removes the residual graphite and binder, and then the alkali solution is added to the powder to dissolve aluminum and aluminum oxides; The filter slag containing lithium and iron was filtered, the molar ratio of iron, lithium and phosphorus in the filter residue was analyzed, iron source, lithium source and phosphorus source were added, and the molar ratio of iron, lithium and phosphorus was adjusted to 1∶1∶1. A new lithium iron phosphate cathode material is obtained by adding a carbon source and calcining in an inert atmosphere after ball milling.

The recycling system is not perfect
The national "863" plan, the "973" plan and the "Eleventh Five-Year Plan" high-tech industry development plan all divide lithium iron phosphate batteries into key support areas, but the battery production technology requirements are relatively strict, resulting in high battery prices, only used in electric motorcycles and a small number of cars. Therefore, automotive power batteries have not yet been scrapped in large quantities, and a systematic professional automotive power battery recycling system has not yet been established. The existing recycling system has certain problems and low recycling efficiency.