Cobalt-free Lithium-rich layered oxides (LRLOs) are promising cathodes for low-cost and high-energy-density Li-ion batteries. However, their remarkable capacity comes with challenges including structural degradation, irreversible oxygen release and sluggish kinetics. Herein, we conduct a one-step dual-modified strategy by yttrium doping and Li 3 PO 4 surface modification. Combining density-functional theory calculations with in-situ X-ray diffraction and in-situ differential electrochemical mass spectrometry, the Y 3+ doping and Li 3 PO 4 nano coating modified LRLOs is demonstrated has an excellent structural stability with enhanced Li⁺ diffusion kinetics and stabilized oxygen lattice. Excellent rate performance and thermal stability are achieved: high discharge specific capacity of 221 mAh·g −1 at room temperature (96.5 % at 1 C after 100 cycles) and incredible discharge specific capacity of 210 mAh·g −1 at 55 °C (91.8 % at 2 C after 100 cycles). This work resolves the safety and stability issues and provides a feasible strategy for Co-free LRLOs.
Jun Pan,Huili Peng,Yehao Yan,Yuzhou Bai,Jian Yang,Nana Wang,Shixue Dou,Fuqiang Huang
Polymer solid-state batteries (SSBs) possess the advantages of good interfacial contact, but their application faces low ionic conductivity. Here, three-dimensional (3D) porous composite polymer electrolytes with propylene carbonate plasticizer (3D-PPLLP-CPEs) fabricated effectively, displaying high ionic conductivity even at room temperature. Electrochemical in-situ polymerization of 3D-PPLLP-CPEs occurs during the first discharge process, avoiding safety issues caused by the liquid plasticizer without sacrificing the ionic conductivity of the electrolyte. Besides, the controllable in-situ generated LiF-enriched interface can avoid the Li dendrite growth. To further promote the practical value of SSBs, micro-sized Si@Li 3 PO 4 @C with high initial Coulombic efficiency was adopted to replace lithium foil. The LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM111)//Micro Si@Li 3 PO 4 @C full cell has achieved capacity of 129.1 mAh g −1 at a current density of 0.2 C, with capacity retention of 98.5% after 100 cycles, which is the best performance based on the Si anode in SSBs. Even at the high current density of 2.0 A g −1 , the capacity remains 92.5 mAh g −1 . This design of CPEs and electrodes has paved a new way to construct practical SSBs.
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