Study On The Modification Of High-capacity Alloyed Anode Materials For Lithium-ion Batteries

Current commercial lithium-ion batteries mainly use graphite as the negative electrode material,but due to its lower theoretical capacity(372 m Ah/g),the energy density of lithium-ion batteries is close to its theoretical limit,which cannot meet and support the future high-end industry’s impact on lithium-ion batteries.Due to the performance requirements of batteries,the development of high-capacity anode materials has become a research hotspot.Among them,alloyed(silicon,aluminum,etc.)anode materials have high theoretical capacity and have good development prospects as anode materials for high specific energy lithium-ion batteries,but the problem of swelling and powdering seriously restricts the application of such materials.To this end,researchers have proposed strategies such as nanometerization,composite structure,three-dimensional porous structure,and coating modification.The coating modification can not only effectively buffer the volume change,but also achieve effective isolation between the active material and the electrolyte,and inhibit the interface side reaction is one of the most effective modification methods at present.In order to improve the coating effect,the development of coating materials with high mechanical strength has become an important research direction.This work proposes a TiAlN coating modification strategy.Firstly,finite element simulation calculations are used to verify the theoretical feasibility of the scheme,and then a TiAlN coating layer is successfully constructed on the surface of the aluminum anode using magnetron sputtering technology.The electrochemical performance test showed that the TiAlN coating modification strategy significantly improved the structural stability of the aluminum anode.Among them,the dual-ion battery system based on aluminum anode is cycled for 900 weeks under 5 C rate conditions,the capacity retention rate reaches 95%,and the cycle life is 3 times longer than that of the unmodified aluminum anode.The test of a full battery assembled with high areal density(7.0 mg/cm~2)traditional cathode materials(lithium iron phosphate,lithium nickel cobalt manganese oxide)positive electrodes once again verified the effectiveness of this strategy.Among them,the full battery based on lithium iron phosphate cathode is Cycling for 400 weeks under the condition of 2 C current density,the capacity retention rate reached 86%.In order to further improve the fracture toughness of the coating layer,this work further proposes a LiPON-Al nanocomposite coating strategy.Finite element simulation calculations show that the addition of metallic Al soft phase to the fast ion conductor phase LiPON can effectively inhibit the propagation of cracks and help improve the strength of the mechanical coating.The electrochemical performance test results show that the dual-ion battery based on the coated modified silicon anode is cycled for 1500 cycles at 10C,and the capacity retention rate is 85%,while showing high rate performance.The full battery constructed with lithium iron phosphate cathode was cycled for 600 cycles at a current density of 0.2 A/g,and the capacity retention rate reached 98%,again verifying the effectiveness of this strategy.