| With the rapid growing of lithium-ion batteries(LIB)in electronics and electric vehicles,the spent lithium ion batteries are increasing exponentially due to capacity degradation.Recycling spent lithium-ion batteries has become an urgent issue,which has aroused widespread concern.Despite tremendous efforts,it is still unsatisfactory to find green ways to economically recycle spent lithium-ion batteries.In this paper,a green and comprehensive recycling method based on the electric field driven de-lithiation is reported.The lithium ions can be effectively recovered from the cathode materials and the de-lithiated electrode materials can be re-utilized as efficient oxygen evolution reaction(OER)catalysts or supercapacitor electrode materials.This recycling method makes full use of the spent electrode materials,with the characteristics of green,economy and high eff-iciency.1.We use LiNixCoyMnzO2 electrode material as anode,a piece of blank carbon cloth as cathode,and NaCl solution as electrolyte to construct an electrolytic cell.When a voltage is applied to the electrolytic cell,lithium ions are extracted from the LiNixCoyMnzO2 electrode material,with simultaneous H2 production.The lithium-deficient electrode material obtained after de-lithiation exhibits excellent catalytic performance for oxygen precipitation reaction(OER).The lithium ions in the solution are recovered by concentrating and precipitation.The effects of electrolysis conditions such as voltage,time,and stirring rate on the de-lithiation process are experimentally studied.The de-lithiated samples exhibit decent electrocatalytic performances due to the electrochemical de-lithiation process that exerts positive effects on tuning the morphology,electronic structure,valence state and crystal structure of the materials.The commercially LiNi0.5Co0.2Mn0.3O2,are chosen as the representative model to verify the feasibility of the strategy.The typical LiNi0.5Co0.2Mn0.3O2 fresh electrode material is chosen for the simulation recovery experiment,and a high delithiation rate of 91.37%is achieved at 2.0 V The Li0.4Ni0.5Co0.2Mn0.3O2 obtained by de-lithiation at 1.5 V as an OER catalyst shows a low overpotential of 236 mV and a small Tafel slope of 66 mV dec"1 at 20 mA cm-2,with excellent stability for more than 80 hours.Meanwhile,we have extended the de-lithiation experiments to spent LiNi0.5Co0.2Mn0.3O2 electrode material.The obtained Li0.45Ni0.5Co0.2Mn0.3O2 material by de-lithiation of the spent LiNi0.5Co0.2Mn0.3O2 at 1.5 V displays remarkable electrocatalytic performance,with a low overpotential of 221 mV,and small Tafel slope of 67 mV dec-1.In addition,the recycling method is also universally applicable to other proportions of ternary cathode materials.2.Similarly,the de-lithiation of LiMn2O4 cathode material is also investigated,with the LiMn2O4 material coated on carbon cloth as the anode,and blank carbon cloth as the cathode.By applying voltage,the lithium ions in LiMn2O4 can be effectively and controllably extracted.When the voltage reaches 3.0 V,the allotropic λ-MnO2 material is finally generated.The lithium manganate material after de-lithiation retains the spinel AB2O4 cube skeleton,but the empty A site becomes the active site,forming a unique open structure with higher electrochemical activity.Re-used as electrode material of supercapacitor,the obtained λ-MnO2 material after de-lithiation shows significantly enhanced electrochemical performance compared with the initial LiMn2O4 material.Among the various of de-lithiated samples,the sample obtained by de-lithiation at 3.0 V has the best electrochemical performance.At a current density of 2 mA cm-2,it realizes an area specific capacity of 382.2 mF cm-2,which is much higher than the initial lithium manganate material’s 159.0 mF cm-2.At the same time,it also presents good rate capability and excellent cycling stability,indicating that the recovered λ-MnO2 material has good electrochemical performance as a supercapacitor electrode material. |
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