One-pot Synthesis Of Phosphorus-based Nanostructured Carbon And Research On Its Lithium Ion Storage Performance

Lithium ions batteries(LIBs)are widely used due to their high energy density,long cycling performance and good rate capability.Basically,LIBs' anode includes graphite,transition metal oxides and titanium-based materials etc.However,these materials have suffered from low specific capacity,poor conductivity and large volume effect.In recent years,phosphide and phosphorus have aroused great interests in application to LIBs due to the high discharge platform which promise to output high energy density.Nevertheless,phosphorus-based anode materials and transition metal phosphides have drawbacks involving volume expansion and collapse during the charge/discharge cycles.Based on these issues,we proposed one-pot synthesis method to prepare phosphorus-based nano-carbon with different structures and explore their characteristics and related working mechanisms as anode materials for LIBs.The specific research contents and results are stated as below:1.The(N,Ni,P)-doped echinus-like carbon nanospheres were prepared and investigated by low-temperature carbonization using nickel-based organic phosphorus framework as precursors.The diameter of the as-prepared carbon nanospheres is about?600 nm.The hierarchical pore structure is beneficial to the intercalation and deintercalation of lithium ions from multiple directions and greatly shortens the diffusion path of lithium ions.Besides,the one-pot synthesis method effectively avoids the generation of harmful gas,i.e.PH3.The calculation of pseudocapacitance ratio shows that the heteroatoms can not only enhance the ion adsorption,but also improve the conductivity of carbon materials.When employed as anode for LIBs,the reversible specific capacity of 386.5 mAh·g-1 can be achieved under the current density of 0.05 A·g-1,demonstrating the superior cycling stability.This excellent performance is attributed to the unique structure of(N,Ni,P)tri-doped porous carbon spheres,which introduce additional capacity due to the existence of "reservoir effect".Further,electrochemical analysis suggests that the surface-limited capacitive behavior favors to improve the lithium storage capacity of porous carbon spheres.2.Heteroatom doping would impact the electronic structure of the host material,leading to the improved energy storage characteristics in doped material.In this chapter,the(N,P)co-,(N,Ni,P)tri-,(N,Co,P)tri-and(N,Ni,Co,P)tetra-doped Porous carbon nanospheres(PCS)were prepared under low-temperature carbonization to examine the insight into lithium ion storage behavior of H-PCS,respectively.It is found that the specific surface area,pore texture and structural defects of H-PCS were dependent on doping of heteroatoms as well as the charge transfer resistance and Li-ion diffusion coefficient.Significantly,the redox reaction potential during the charge/discharge could be mediated upon the doping.Thus,when evaluated as anode for LIBs,the(N,Ni,Co,P)doped PCS exhibited highly reversible capacity of 680 mAh·g-1 at 0.1 A·g-1,excellent rate capability(115.9 mAh·g-1 at 1.0 A·g-1)and superior cycling performance(399.6 mAh·g-1 after 100 cycles at 0.1 A·g-1).Moreover,the cyclic voltammogram measurements highlighted that the doping of metal atoms is favor forimproving the capacitive contribution of surface limited diffusion.3.In this chapter,the carbon-coated Ni2P nanoparticles embedded in echinus-like porous carbon(Ni2P@C@EPC)have been synthesized by employing nickel-based metal organophosphorus skeleton as precursor.The Ni2P@C@EPC plays a significant role in realizing high and stable performance by confining the reaction between Ni2P and Li+,facilitating Li+ diffusion mobility and inhibiting the volume change in charge/discharge.As a result,the Ni2P@C@EPC demonstrates high specific capacity of 807.7 mAh·g-1 at 0.2 A·g-1,excellent rate capability(592.1,455.9,346.1,236.4 and 160.69 mAh·g-1 at 0.1,0.2,0.5,1.0 and 2.0 A·g-1),and long cycling stability(464.8 mAh·g-1 at 0.2 A·g-1 after 100 cycles).Moreover,the structure evolution upon cycling as well as electrochemical analysis has suggested that the Ni2P@C@EPC anode should be a potential candidate for high-performance LIBs'anode.