| Lithium-ion battery,which has a great market share in mobile phones,laptops and other fields,is a new generation of secondary battery which is developing rapidly in the 1990 s.Cathode material is one of the key materials for making lithium-ion battery.Compared with other cathode materials,Li Co O2,which has large applications in lithium-ion battery,has the best comprehensive performances in reversibility,discharge capacity,charge efficiency,voltage stability,etc.After a long period of utilizing,the microstructure of the anode material Li Co O2 will be changed,such as the changes of surface composition,valence change of Co3+,the cell parameters change of Li Co O2.As a result,the electrochemical capacity of lithium ion batteries is largely decreased.The research on the repair of the Li Co O2 microstructure of the anode material in the spent lithium ion battery is beneficial to the promotion of the high cost and low efficiency of the large number of failed Li Co O2.This paper puts forward a new method of "surface chemical stripping-remediation" to study the repair of Li Co O2 electrode components,which is different from other scholars.The changes of mass-heat,phase composition,morphology of the roasting product,elements distribution,the electron bonding energy of Co element,and phase composition,morphology,unit cell parameter of repaired Li Co O2 were studied by TG-DSC,XRD,SEM,EDS,XPS and ICP.The results showed that:?1?Using Na HSO4·H2O as chemical stripping reagent,Li Co O2 and Na HSO4·H2O were uniformly mixed with 1:0.01,1:0.05,1:0.1 molar ratio roasted,the roasted product was dissolved in water and filtered,Li2CO3 was added to the residue by the amount of n?Li/Co?of 0.75,1.06,1.5,after high temperature roasting,the recovered Li Co O2 electrode material was obtained.Results showed that:The optimum experimental conditions were Li Co O2:Na HSO4·H2O=1:0.05 and n?Li/Co?=1.06,after the repair experiment,the lithium element was no longer missing and the phase composition was?018??110??006??012?peaks appear Li Co O2 a substance,the repaired of Li Co O2 is better in the Li+ embedding and detachment capacity and is a layered structure.I?003?/?104?=3.67,I?006?/?104?=0.92,I?006?/?003?=0.04,the degree of crystallization,purity and cycle life are all better,a???=2.8190,c???=13.9041,c/a=4.9323,very close to the commercial Li Co O2 value.The repaired of Li Co O2 exhibited irregular shapes and nonuniform distribution.?2?Using K2S2O7,Na2S2O7 as chemical stripping reagent,Li Co O2 and K2S2O7,Na2S2O7 were uniformly mixed with 1:0.5,1:1,1:1.5 molar ratio roasted,the roasted product was dissolved in water and filtered,Li2CO3 was added to the residue by theamount of n?Li/Co?of 1.06 after high temperature roasting,the recovered Li Co O2 electrode material was obtained.Results showed that: The convert ratio of Li Co O2 had proportional relation with the K2S2O7,Na2S2O7 content.When the ratio of Li Co O2 to K2S2O7,Na2S2O7 is 1:1.5,the conversion rate arrived to 100%.The roasting products exhibited irregular shapes,nonuniform distribution and the structure is more compact.With the increase of K2S2O7,Na2S2O7 content,the elements of Co,Na,K,O and S in the roasting products were mostly diffuse distribution and the electron bonding energy of Co was increased.The electron binding energy of Co element in the dried residue after calcination of Li Co O2 and K2S2O7,Na2S2O7 is about the same as that of Co element in Li Co O2,the Co element electron binding energy peak strength and peak shape sharp with the increase of K2S2O7,Na2S2O7 content in the mixtures of Li Co O2 and K2S2O7,Na2S2O7.The main material was Li Co O2 and Co3O4 and the repair of Li Co O2 was a layered structure when the Li Co O2 and K2S2O7 K2S2O7,Na2S2O7 were roasted in different proportions. |
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