| The rapid development of electric vehicles has stimulated the study of lithium-ion batteries with high capacity and energy density.Due to the high specific capacity(>250 m Ah g–1)and working voltage,lithium-rich manganese-based cathode materials have become a promising cathode material for realizing high-energy-density batteries.Nevertheless,Li-rich materials still face serious voltage attenuation,dissolution of transition metals and poor rate property during cycling.Considering the importance of binder in the electrode,this paper has developrd novel water-based binders to match with Li-rich material Li[Li0.2Co0.13Ni0.13Mn0.54]O2（NCM）to realize the regulation and construction of high-performance lithium-rich cathode,and has studied the effect and mechanism of binder on the performance of lithium-rich cathode.The main contents are as follows:（1）Lithium polyacrylate（LiPAA）has been selected as a novel binder to assist the construction of lithium-rich NCM cathode.By adjusting the mass ratio of LiPAA（2.5%,5%,7.5%,10%）in the electrode,the electrode can be regulated.The effect and mechanism of different binder contents on voltage fade and electrochemical performance of lithium-rich materials have been studied.It is found that when the addition amount is 5%,the prepared LiPAA5 binder electrode has the best charge-discharge performance.Its initial discharge specific capacity at 0.2 C rate is 224.7 m Ah g–1.After 50 cycles,the discharge voltage of LiPAA5 binder electrode only decays by0.117 V.That is,the voltage attenuation of lithium-rich materials has been effectively alleviated.The-COOH in the structure of LiPAA can form a strong hydrogen bond with the oxygen atom of lithium-rich material,which makes a strong adhesion between the active material and the binder.（2）Xanthan gum（XG）has been selected as a new binder to assist the construction of lithium-rich NCM cathode.The electrode structure was regulated by adjusting the mass ratio of XG（2.5%,5%,7.5%,10%）.The impact mechanism of different XG amounts on the stability and electrochemical performance of the electrodes have been studied.When the added amount of XG is 5%,the capacity and cycle performance of the constructed XG5 binder electrode is the best.After 50 cycles at 0.2 C rate,the electrode can still provide a reversible discharge specific capacity of 203.2 m Ah g–1.The capacity only decreases by 8.8%,and the voltage only decreases by 0.186 V.This is because XG as a binder can form chemical bonds with the surface of lithium-rich active particles and provide a large number of active sites,thereby stabilizing the combination of electrode components.（3）By mixing two binders（XG and LiPAA）and adjusting their mass ratio（1:1,1:2 and 2:1）,the construction of lithium-rich NCM cathode has been realized.The effect and mechanism of composite binder on the electrochemical performance of lithium-rich NCM cathode have been studied.It is found that when the ratio of XG:LiPAA is 2:1,the constructed AG21-10%binder electrode exhibits the highest initial discharge specific capacity and the best cycle performance.Compared with LiPAA,the reversible specific capacity of the AG21-10%binder electrode increases by 16.7 m Ah g–1,and the capacity retention increases by 16.44%after 100 cycles at 0.2 C rate.In addition,the voltage of AG21-10%binder electrode decreases by only 0.199 V after100 cycles,demonstrating the effectively suppression of the voltage fade of lithium-rich materials.In the composite binder,LiPAA can provide extra Li+ions for electrode circulation,and XG can produce firm adhesion with electrode materials.The synergistic effect of the two binders further improves the cycle stability of the lithium-rich cathode. |
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