The need to develop safe solid-state lithium batteries has stimulated intense research efforts for Li + solid electrolytes. However, the low conductivity limits the development of NASICON LiZr 2 (PO 4 ) 3 (LZP) electrolyte. Here, the doping effects of Ta on the structure, surface morphologies and electrochemical properties of Li 1- x Zr 2- x Ta x (PO 4 ) 3 (LZTP, x = 0, 0.01, 0.02, 0.04, 0.06 and 0.08) solid electrolyte were analyzed. LZTP was prepared using a simple solid-state reaction route, followed by sintering at 1200 °C for 12 h. A proper content of Ta 5+ substitution for Zr 4+ is beneficial to stabilize the high conductive rhombohedral (α) phase of LZP at room temperature. Doping Ta 5+ is conducive to unblocking of Li + at the M1 site and facilitates the occupation of Li + at the M2 site, thereby expanding the pathway for Li + conduction. Rietveld refinement data demonstrated that the Zr–O and P–O bond lengths ( d Zr-O and d P-O ) increased with a decrease in Zr–O–P bond angles ( θ Zr-O-P ) as x rose. The distortions in the ZrO 6 octahedron may weaken the coulomb attraction in Li + -O 2- , resulting in a lower activation energy ( E a ) and a higher Li + conductivity. The highest room-temperature conductivity (6.06 × 10 −5 S cm −1 ) was obtained at x = 0.06, which reached 1.5 × 10 −4 S cm −1 at 50 °C. The E a was found to decrease from 0.388 eV ( x = 0) to 0.306 eV ( x = 0.06). In addition, Ta doping resulted in improved connectivity and reduced pore formation, which also contributed to the decrease in resistance. The Raman spectrum demonstrated that some phonon modes of bending vibration in PO 4 were degenerate and external modes became too weak to be observed or even disappeared as Ta content increased. This change in the modes also had an impact on the Li + conductivity. Overall, the LZTP-0.06 appears to be a promising candidate for the solid electrolyte.
Kai Chen,Yanping Tang,Shuqing Zhang,Xuxia Hao,Xiaoning Zhao,Li-Qian Cheng,Youxuan Xiao,Zhaoyin Wen
Sulfide all-solid-state lithium battery (ASSLB) with nickel-rich layered oxide as the cathode is promising for next-generation energy storage system. However, the Li+ transport dynamic and stability in ASSLB are hindered by the structural mismatches and the instabilities especially at the oxide cathode/sulfide solid electrolyte (SE) interface. In this work, we have demonstrated a simple and highly effective solid-state mechanofusion method (1500 rpm for 10 min) to combine lithium conductive NASICON-type LiZr2(PO4)3 nanocrystals (∼20 nm) uniformly and compactly onto the surface of the single crystallized LiNi0.8Co0.1Mn0.1O2, which can also attractively achieve Zr4+ doping in NCM811 and oxygen vacancies in the LZPO coating without solvent and annealing. Benefiting from the alleviated interface mismatches, sufficient Li+ ion flux through the LZPO coating, promoted structural stabilities for both NCM811 and sulfide SE, strong electronic coupling effect between the LZPO and NCM811, and enlarged (003) d-spacing with enriched Li+ migration channels in NCM811, the obtained LZPO-NCM811 exhibits superior stability (185 mAh/g at 0.1C for 200 cycles) and rate performance (105 mAh/g at 1C for 1300 cycles) with high mass loading of 27 mgNCM/cm2 in sulfide ASSLB. Even with a pronounced 54 mgNCM/cm2, LZPO-NCM811 manifests a high areal capacity of 9.85 mAh/cm2. The convenient and highly effective interface engineering strategy paves the way to large-scale production of various coated cathode materials with synergistic effects for high performance ASSLBs.
Yanqing Lai,Zhen Sun,Liangxing Jiang,Xiaojing Hao,Ming Jia,Li Wang,Fangyang Liu
NASICON-type LiZr 2 (PO 4 ) 3 (LZP) has a high bulk ionic conductivity (∼10 −4 S cm −1 ) and a wide electrochemical stability window between 0 and 5.5 V. However, LZP suffers from a problem in which its desirable rhombohedral phase transforms to the triclinic phase (∼10 −8 S cm −1 ) below 50 °C. In this work, we reported a rhombohedral-structured LiZr 2 (PO 4 ) 3 (α-LZP) at room temperature with a high total Li-ion conductivity (2.8 × 10 −6 S cm −1 ) by a microwave sintering process. Moreover, this approach realized a drastic reduction in the sintering temperature from the typical 1200 °C–900 °C with only a 4 h holding time. Using this approach, we also demonstrated the successful synthesis of Ca-incorporated Li 1.2 Ca 0.1 Zr 1.9 (PO 4 ) 3 (LCZP) with an ionic conductivity of 1.7 × 10 −5 S cm −1 .
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