A uniform and high-voltage stable LiTMPO4 coating layer enabled high performance LiNi0.8Co0.15Mn0.05O2 towards boosting lithium storage

Abstract

LiTMPO₄ materials, such as LiNiPO₄, can maintain structural stability and Li⁺ transport activity up to 4.8 V, showing great potential to stabilize layered nickel-rich cathodes at high voltage. But achieving a uniform LiTMPO₄ coating layer remains a great challenge. Herein, an ultrathin and uniform LiTMPO₄ layer (mainly LiNiPO₄) is successfully coated on the surface of LiNi_0.8Co_0.15Mn_0.05O₂ (NMC@LTMP) via utilizing the surface chelation of phytic acid with NMC precursors and a subsequent high-temperature in situ reaction. The reconstructed surface and interface could act as stable paths for Li⁺ transport and efficient barriers against electrolyte corrosion. Thus, harmful side reactions like solid electrolyte interphase overgrowth, irreversible phase transformation, and metal dissolution are inhibited simultaneously. Impressively, the optimized NMC@LTMP2 cathode exhibits remarkably improved capacity, as high as 215 mA h g⁻¹ at 2.8–4.5 V, with capacity retention of 87.21% after 200 cycles and outstanding rate capability of 140 mA h g⁻¹ at 10C, significantly better than a pristine cathode. Furthermore, a pouch cell assembled with an NMC@LTMP2 cathode and graphite anode also exhibits robust capacity retention of 82.42% after 100 cycles. These results provide useful insights towards enabling the application of NMC cathodes via developing facile modification methods.