Research And Development Of New Rare Earth-based Lithium-ion Battery Anode Materials

In recent years,graphite,the main commercial material of lithium-ion batteries,cannot meet the increasing commercial demand for the performance of electrode materials in terms of electrochemical performance,and lithium dendrites may form during the operation of its lower operating voltage platform,which may present hidden dangers.The "zero-strain"lithium titanate anode material with a high voltage platform(about 1.5V vs Li/Li+)can also guarantee the safety performance,so it has become a popular object to be studied.Despite the above advantages,its higher lithium-plated platform also results in lower energy density.In order to increase the energy density and meet the needs of contemporary anode materials,LiEuTiO4 with Ruddlesden-Popper structure has entered people’s sight.LiEuTiO4 has a higher capacity and stability of lithium titanate,and has a lower charge-discharge platform(0.8 V vs.Li/Li+).However,LiEuTiO4 also faces the characteristics of low ion conductivity and poor rate performance.This article explores LiEuTiO4 from two aspects:synthesis path and doping modification.Summarized as follows:(1)A layered perovskite-structured NaEuTiO4 was synthesized by a sol-gel method,and was acid-treated with dilute nitric acid.It was found that the sodium ions in NETO will gradually dilute the hydrogen ions in nitric acid with the increase of pickling time.The exchanged compounds can be reversibly exchanged with lithium ions,and there is an ion exchange path as Na+→H+→Li+,which shows a good lithium intercalation/deintercalation behavior.Through SEM and TEM observations,we found that dilute nitric acid will react with the sample and leave grooves on the surface.It is interesting that the sample etched during the electrochemical cycle shows a self-repairing state,while the cycling performance(acid The 12-hour sample has a specific discharge capacity of 213.2 mA g-1 in the first cycle,retention rate maintain 117.9%after 300 cycles capacity)and the rate of dischargeability performance(with a discharge current density of 2000 mA g-1,the HETO-12hrs sample can still maintain 149.4 mA h g-1)has been improved.The above preparation ideas not only provide us with the possibility and feasibility of designing and screening rare earth-based titanates as key electrode materials for new energy storage devices,but also for the extraction of lithium in the future and a whole new idea of recycling.Therefore,it is very necessary to study the ion exchange behavior and electrochemical characteristics of materials with layered perovskite structure,such as NaLnTiO4.(2)Based on the synergistic effect of Eu3+and Ce3+,LiEuTiO4 synthesized by the sol-gel method was modified by Ce3+doping.We selected cerium nitrate hexahydrate as the Ce source and doped LiEuTiO4.The structure and morphology electrochemical properties of LiCexEu1-xTiO4 after doping were studied.The results show that adding cerium nitrate hexahydrate during the synthesis process can indeed dope Ce ions into LiEuTiO4.The introduced cerium ion improves the ionic conductivity of the material.Moreover,it also improves the electrochemical performance of the material.Cyclic stability of LiEu0.995Ce0.005TiO4 samples(specific discharge capacity at the first cycle of 178.9 mA h g-1,after 200 cycles at 93.9%capacity retention rate),rate performance(discharge capacity at 1000mA g-1 is still 122.8 mA h g-1)was significantly better than the undoped sample.It shows that the introduction of Ce ions has achieved the expected results.