Dual modification of LiNi_(0.83)Co_(0.11)Mn_(0.06)O_(2) cathode materials by K^(+) doping and Li_(3)PO_(4) coating for lithium ions batteries

Li_(3)PO_(4)@Li_(0.99)K_(0.01)Ni_(0.83)Co_(0.11)Mn_(O.06)O_(2)(NCM-KP) cathode powders are synthesized via K^(+)doping in calcination processes and H_3PO_4 coating in sol-gel processes.K^(+) precisely enters into the lattice to widen the(003) plane to 0.4746 nm with a lower cationic disordered degree of 1.87%.Moreover,the surface residual lithium salts are treated by H_3PO_4 to generate a uniform Li_(3)PO_(4) coating layer of approximately 11.41 nm,which completely covers on the surface of secondary spherical particles to improve the interfacial stability.At 25℃,the NCM-KP electrode delivers a discharge specific capacity of 148.9 mAh·g^(-1) with a remarkable capacity retention ratio of 84.1% after 200 cycles at 1.0C and retains a high reversible specific capacity of 154.4 mAh·g^(-1) at 5.0C.Even at 1.0C and 60℃,it can maintain a reversible discharge specific capacity of 114.6 mAh·g^(-1) with 0.21% of capacity decay per cycle after 200 cycles,which is significantly lower than 0.40% for the pristine NCM powders.Importantly,the charge transfer resistance of 238.89 Ω for the NCM-KP electrode is significantly lower than 947.41 Ω for the pristine NCM one by restricting the interfacial side reactions.Therefore,combining K+doping and Li_(3)PO_(4) coating is an effective strategy to enable the significant improvement of the electrochemical property of high-nickel cathode materials,which may be mainly attributed to the widened diffusion pathway and the formed Li_(3)PO_(4) protective layer,thus promoting Li~+diffusion rate and preventing the erosion of HF.

High-performance sandwiched hybrid solid electrolytes by coating polymer layers for all-solid-state lithium-ion batteries

Poly(vinylidenefluoride-co-hexafluoropropylene)(P(VDF-HFP))/Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP)/P(VDFHFP) sandwiched hybrid solid electrolytes were precisely tailored and successfully fabricated to assemble into allsolid-state lithium-ion batteries,which were systematically evaluated on microstructure,morphology,thermal stability and electrochemical performance.The sandwiched hybrid solid electrolytes can achieve intimate contact with cathode and anode electrodes to present an excellent interfacial stability.Furthermore,the sandwiched hybrid solid electrolytes possess flexible surface,wide electrochemical working window of 4.7 V,high ionic conductivity of 0.763 mS·cm^(-1) and high thermal stability of 460℃,which may contribute to realizing the practical application in all-solid-state lithium-ion batteries.The assembled cells with the hybrid solid electrolytes can quickly stabilize at a specific discharge capacity of 145.4 mAh·g^(-1) at 0.1 C after only 5 cycles and present admirable rate performance.In addition,morphology characterizations of the sandwiched hybrid solid electrolytes after long-term cycles show a relatively integrated structure coating with a compact LATP layer.The investigations afford a promising strategy that the sandwiched hybrid solid electrolytes can overcome the mechanical limitations of the interface between electrodes and inorganic solid electrolytes to provide favorable properties for all-solid-state lithium-ion batteries.