Application And Fabrication Of New Type Carbon Nanotube As Conductive Additives In Lithium-ion Battery

Carbon nanotubes?CNTs?are gradually replacing carbon black to play an important role in lithium ion batteries?LIBs?owing to its unique mechanical,electrical and thermal properties.The state-of-the-art CNT conductive additive in LIBs has two challenges:first,the metal catalyst residue in CNT conductive additive causes the inner short circuit in the electrochemical process of LIBs;second,the built conductive network of CNTs could not sustain the volume variation of electroactive materials in the high rate charge-discharge process for the long cyclicity.To solve these two problems,the ultra-high-purity carbon nanotubes and the hybrid carbon nanotubes?H-CNTs?were introduced for the conductive additive to improve the cycle performance and rate performance of LIBs.The main research contents are summarized as follows:?1?A water-assisted chemical vapor deposition?CVD?device was built to realize the scale preparation of the vertically aligned carbon nanotubes?VACNTs?with the ultra-high purity?>99.99%?.Based on the optimized catalytic system,VACNT with uniform diameter and controllable structure performance was obtained,and the daily output of over 1 gram was achieved.?2?The CNT dispersion parameters were optimized in the ultrasonic and ball milling methods for the conductive additive preparation,the as-prepared sample was used in the LiFePO₄ LIBs.The electrochemical performance?5 C:140 mAh/g,10 C:109 mAh/g?is better than the conventional ones?5 C:100 mAh/g,10 C:0 mAh/g?.?3?The H-CNTs were synthesized by a fluidized bed process in the assistance of a designed Ni-Mn-Al catalyst.The small diameter?¹0 nm?and large diameter?⁵0 nm?CNTs were used in the conductive additive for the SnO₂ LIBs to testify the idea.The H-CNTs battery exhibits an excellent cycling performance?1 A/g 1000 cycles:710 mAh/g?and rate capability?10 A/g:400 mAh/g?.The conventional CNTs battery is much lower?10A/g:200 mAh/g?.The characterization results show the H-CNTs conductive network remained stable after the tests.