Research On The Recovery Of High Value-added Lithium And Cobalt From Spent Lithium-ion Batteries

In recent years,with the rapid development of portable electronic devices and new energy vehicles,lithium-ion batteries have been widely used in these fields as a rechargeable battery.The lithium-ion battery production in China has reached nearly16 billion in 2019.In view of the limited service life of lithium-ion batteries,we will have to face a large number of spent lithium-ion batteries in the near future.Lithium-ion batteries contain a variety of valuable metal elements,among which lithium and cobalt are high value rare metals,and the content is much higher than natural ores.Therefore,research on the recovery of lithium and cobalt from spent lithium-ion batteries has important socio-economic value.At present,lithium is mainly recovered from waste lithium-ion batteries by sodium carbonate precipitation method,so that lithium is recovered in the form of lithium carbonate,which has some problems such as long process and low recovery rate.In this paper,a new process of hydrogen reduction-water leaching is proposed to recover lithium from cathode materials in the form of lithium hydroxide.Firstly,the thermodynamic calculations of lithium cobalt oxide（Li Co O₂）and ternary materials(Li Ni_1/3Co_1/3Mn_1/3O₂,LNCM)in hydrogen atmosphere were carried out.The results show that CO,Ni,Mn O and Li OH are the most stable reduction products under a wide range of thermodynamic conditions.The reduction behaviors of Li Co O₂ and LNCM in hydrogen atmosphere were investigated.The results showed that Li Co O₂ and LNCM were successfully reduced at 450℃for 1 h.The lithium in Li Co O₂ and LNCM was completely converted into soluble Li OH.Then the effects of liquid-solid ratio,leaching temperature and leaching time on the water leaching efficiency of reduction products were investigated.The results show that the leaching rate of lithium in Li Co O₂ reduction product is more than 99.9%when the liquid-solid ratio is 300 g/L,the leaching temperature is 30℃and the leaching time is 30 min.When the liquid-solid ratio is 300 g/L,the leaching temperature is 30℃,and the leaching time is 10 min,the lithium leaching rate of LNCM reduction product is more than 99.9%.Finally,the Li OH with high purity was obtained by evaporation crystallization.At present,the cobalt in spent lithium-ion batteries is mainly recovered by wet leaching extraction.A method of directly preparing fibrous cobalt powder from lithium cobalt oxide cathode material for high performance microwave absorbing material is proposed in this paper.Firstly,Li Co O₂ cathode powders were leached by oxalic acid at 60℃for 1 h,and then heated to 80℃for 1 h.The fibrous precursor of cobalt oxalate with uniform morphology was prepared,and the leaching rate was more than 90%.The porous fiber cobalt powder was prepared by thermal decomposition of the cobalt oxalate precursor in nitrogen atmosphere at 420℃,with a diameter of 1-2μm,each fiber was composed of small particles with a size of 100-200 nm.When the sample thickness is 4.5 mm,the reflection loss（RL）reach-36.14 d B and-38.20 d B at 4.16 GHz and 17.60 GHz,respectively.The frequency range of RL<-10 d B is 3.36–7.44 GHz and 16.56–18.0 GHz,and the effective bandwidth reaches up to 5.52 GHz.