Nanocomposite Materials Based On Alloying Reaction Mechanism As Anode For Lithium/Sodium Ion Batteries

In the 21st century,energy crisis and environmental pollution have been a sensitive and urgent problem.Lithium-ion batteries,as new and efficient energy storage systems,have been successfully used in small electronic devices.The anode materials?graphite?of lithium-ion battery cannot meet the large-scale equipments demand due to its inherent low energy density.One of the key strategies for solving this problem is development of the high-capacity anode materials for lithium-ion batteries.The application of lithium-ion batteries is further limited in large-scale energy storage equipment by the uneven distribution of resources.Compared with lithium-ion battery,low energy density sodium ion battery is very suitable for large-scale energy storage equipment due to the natural abundance,lower price.However,the direct utilization of the well-developed lithium-ion battery graphite anodes for soddium-ion battery turns out to be unsuccessful because of the mismatch of graphite lattice and sodium ion.Therefore,it is crucial to develop robust anode materials with high specifc capacity and long cycling life toward practical applications.In the anode materials of lithium/sodium ion batteries,the alloy-based nanocomposites have great potential for application due to their higher theoretical specific capacity and better safety,especially tin-based sulfides,bismuth-based and selenium-based materials.For example,the theoretical specific capacity of Sn is 847 mA h g^-1,the theoretical specific capacity of Bi is 3765 mA h cm^-3,and the theoretical specific capacity of Se is 3253 mA h cm^-3.They will possess volume expansion problems in the charge and discharge processes,such as the volume expansion rate of tin-based materials reached 358%in the process of alloy-dealloying.The pulverization aroused by the volume variation will lead to serious capacity decay.In this paper,two strategies are adopted to solve these issues.First,wrapping or combining these materials with carbon materials is implemented,which can not only accommodate volume change,but also increase electrical conductivity.Second,specific structural designs have been adopted,which could shorten the diffusion of ion path and be favor for ion/mass transport,ultimately enhance their electrochemical performance.The contents of these works are as below:?1?Nanoconfined SnS in 3D interconnected macroporous carbon as durable anodes for lithium/sodium ion batteries:Nanoconfined SnS in 3D interconnected macroporous carbon?3D SnS/C?has been produced using silica opals as template following a carbonization and sulfuration route.The electrochemical properties of the 3D SnS/C were examined comprehensively as anode materials for lithium/sodium ion batteries?LIBs/SIBs?.It delivers a high specific capacity of 869 mA h g^-1 at 1 A g^-1after 1000 cycles in LIBs and 400 mA h g^-1 at 100 mA g^-1 after 100 cycles in SIBs.The rate performance is also excellent(550 mA h g^-11 at 3 A g^-1 in LIBs and 220.9 mA h g^-11 at 5 A g^-1 in SIBs).The outstanding electrochemical performance of the 3D SnS/C is ascribed to its 3D porous carbon interconnected structure and broad nanoconfined SnS distribution nanoparticles in carbon matrix,which not only improve the conductivity,but also keep the structure integrity,and as a result of enhancing the cycling stability of the material.In addition,this facile and novelty strategy can be potentially utilized for preparing other 3D transition metal sulfides/interconnected macroporous carbon composite for energy storage.?2?Bismuth nanorods encapsulated in nitrogen-doped carbon nanotubes as long cycling and high rate anode for sodium-ion batteries:Here we present rational synthesis of bismuth nanorods encapsulated in N-doped carbon nanotubes?Bi@N-C?using Bi₂S₃ nanobelts as the template for high-performance SIB.The Bi@N-C electrode delivers superior sodium storage performance in half cells,including a high specific capacity(410 mA h g^-1 at 50 mA g^-1),long cycling lifespan?1000cycles?,and superior rate capability(368 mA h g^-1 at 2 A g^-1).When coupled with homemade Na₃V₂?PO₄?₃/C in full cells,this electrode also exhibits excellent performances with high power density of 1190 W kg^-1and energy density of 119 W h kg^-1_total.The exceptional performance of Bi@N-C is ascribed to the unique nanorod@nanotube structure,which can accommodate volume expansion of Bi during cycling and stabilize the solid electrolyte interphase layer and improve the electronic conductivity.?3?Selenium/mesoporous carbon composite as long cycling and high rate anode for sodium-ion batteries:Se is impregnated into mesoporous carbon sphere?Se/MCS?with a simple way as an anode material for Na-ion batteries.The unique structure of the Se/MCS is benefcial to alleviate the volume change of Se during cycling,improve the utilization of active material.The Se/MCS electrode exhibits high capacity(367 mA h g^-1 at the 100^th cycle at 0.05 A g^-1)and excellent rate capability(268 mA h g^-1 at 3 A g^-1)for Na-ion batteries.In addition,it also shows long cycle life(280 mA h g^-1 at the 1500^th cycle at 1 A g^-1).When coupled with homemade Na₃V₂?PO₄?₃/C in full cells,this electrode also exhibits superior rate capability(100 mA h g^-1 at 3 A g^-1).