Revealing the Ultrahigh Rate Performance of the La and Ce Co-doping LiFePO₄ Composite

Abstract

LiFePO4 with ultrahigh rate ability and enhanced electronic/ionic conductivity can be achieved by element doping. However, the role of substitution on the electronic/ionic conductivity and size effect on the electrochemical performance are still open. Here, LiFePO4 particles (LC-LFP) with tuned sizes are synthesized via La and Ce co-doping, delivering a capacity of 91.9 mAh g–1 under 200 C. In addition, LC-LFP exhibit a power density as high as 57.6 kW kg–1 when the energy density is nearly 300 Wh kg–1 owing to the 105 enhancement of inherent conductivity and 105 Li+ diffusion ability. DFT results suggest that La and Ce co-doping would not only facilitate free Li+ ions to extrude out of the unit cell due to the structure distortion but also generate extra middle-gap states to boost the carrier concentration. Furthermore, it appears that atoms on the surface of the particles tend to decrease the band gap and lower the conduction band compared to the atoms in the bulk. This work demonstrates and discloses a promising strategy to enhance the rate performance of LiFePO4 by element co-doping.

Enhanced Li-Ion Diffusivity of LiFePO4 by Ru Doping: Ab Initio and Machine Learning Force Field Results

“…5,7−9 The poor ionic diffusivity limits electrochemical performance as evidenced by low power density and low capacity retention during charging/discharging, leading to reduced cycle life and low charge/discharge rates. [5][6][7][8]10,11 Increasing the electronic conductivity and Li-ion diffusivity is essential for improving the rate performance of high-power rechargeable batteries.…”

“…However, its practical capacity is low (∼110 mA h g –1 ) even at low current densities of about 2 mA/g; this capacity decreases further at increased current rates, suggesting limited applicability for both low- and high-power rechargeable batteries. Low values of practical capacity are due to its poor electronic conductivity (∼10 –9 to 10 –10 S cm –1 ) and low Li-ion diffusivity (∼10 –12 to 10 –14 cm 2 s –1 ). ,− The poor ionic diffusivity limits electrochemical performance as evidenced by low power density and low capacity retention during charging/discharging, leading to reduced cycle life and low charge/discharge rates. − ,, Increasing the electronic conductivity and Li-ion diffusivity is essential for improving the rate performance of high-power rechargeable batteries.…”

“…The literature on the doping of LFP includes primarily experimental studies ,,,− along with few theoretical studies − including large materials genomics type of study involving multiple dopants . While these studies aim to show that suitable dopants can improve electrochemical performance, a detailed understanding of the effect of doping leading to performance enhancement remains unclear.…”

Interfacial Coupling‐Induced Pseudocapacitance in LiFePO4@Polypyrrole Heterostructures Toward High‐Rate Lithium Storage

“…[3][4][5] However, LFP materials suffer from the slow lithium ion diffusion rate and low electronic conductivity, [6] resulting in poor high-rate performance and greatly hindering its extensive applications on electric vehicles and hybrid electric vehicles. In order to solve these issues, some strategies have been developed such as particle nanosizing, [7,8] elemental doping [9][10][11][12] and hybridization with conductive materials, [13] and surface coating. [14][15][16][17][18][19][20][21] Reducing particle size can effectively shorten the diffusion length, thus enhancing high rate performance.…”

“…[7,8] However, compared with bulk materials, the employment of LFP nanocrystallites in batteries usually suffers from several disadvantages such as decreased tap density and volumetric energy density and poor cycling stability. Issues with low intrinsic electrons can be solved partially by doping with various cations [9][10][11][12] and hybridization with conductive materials [13] and carbon coating. [14] Unfortunately, high-rate capacity performance of LFP is still unsatisfactory because of the intrinsically slow solid-state lithium diffusion.…”