蛋黄壳结构FeF3·0.33H2O@N掺杂碳纳米笼正极材料的构筑及其电化学性能OA北大核心CSTPCD

FeF3·0.33H2O possesses the characteristics of high theoretical capacity and high voltage,but its electrochemical cycling performance is unsatisfactory due to its poor conductivity and serious volume change during redox reaction,resulting in limited application.In this study,by using the strategies of dopamine self-assembly coating,carbonization,HCl etching and HF fluorination,the yolk-shell structured composite FeF3·0.33H2O@carbon nanoboxes(FeF3·0.33H2O@CNBs)composed of N-doped graphene shell and nanocube FeF3·0.33H2O core was synthesized.Its particle size is about 250 nm and thickness of carbon shell is 30-40 nm.FeF3·0.33H2O@CNBs displays an initial charge-discharge capacity of 208 mAh·g-1 at a current density of 0.2C(1C=237 mA·g-1).After 50 cycles,the capacity remains 173 mAh·g-1,and the capacity attenuation rate per cycle is only 0.3%.In comparison,the initial capacity of bare FeF3·0.33H2O is 112 mAh·g-1,and after 50 cycles,only 95 mAh·g-1 reserves,indicating superior cycle performance of FeF3·0.33H2O@CNBs.Furthermore,charging and discharging results at 0.1C-1C show that the rate performance is also significantly better than bare FeF3·0.33H2O.It's due to that N-doped graphene shell prepared by this strategy provides good electron/ion transport performance.At the same time,the carbon shell can not only buffer and inhibit the volume change of the core FeF3·0.33H2O,but also shorten the ion migration distance and improve the Li+ migration rate on the electrolyte storage and retention performance of the electrolyte.As a result,the electrochemical performances are better than those of previous literature.