Abstract
Composite positive electrode materials (1−x) LiNi0.8Mn0.1Co0.1O2∙xLi2SO4 (x = 0.002–0.005) for Li-ion batteries have been synthesized via conventional hydroxide or carbonate coprecipitation routes with subsequent high-temperature lithiation in either air or oxygen atmosphere. A comparative study of the materials prepared from transition metal sulfates (i.e., containing sulfur) and acetates (i.e., sulfur-free) with powder X-ray diffraction, electron diffraction, high angle annular dark field transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electron energy loss spectroscopy revealed that the sulfur-containing species occur as amorphous Li2SO4 at the grain boundaries and intergranular contacts of the primary NMC811 crystallites. This results in a noticeable enhancement of rate capability and capacity retention over prolonged charge/discharge cycling compared to their sulfur-free analogs. The improvement is attributed to suppressing the high voltage phase transition and the associated accumulation of anti-site disorder upon cycling and improving the secondary agglomerates’ mechanical integrity by increasing interfacial fracture toughness through linking primary NMC811 particles with soft Li2SO4 binder, as demonstrated with nanoindentation experiments. As the synthesis of the (1−x) LiNi0.8Mn0.1Co0.1O2∙xLi2SO4 composites do not require additional operational steps to introduce sulfur, these electrode materials might demonstrate high potential for commercialization.
Highlights
The production of battery-electric (EVs) and hybrid-electric vehicles (HEVs) has intensively grown since they provide ecologically more friendly transportation
A comparative study of the materials prepared from transition metal sulfates and acetates with powder X-ray diffraction, electron diffraction, high angle annular dark field transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electron energy loss spectroscopy revealed that the sulfur-containing species occur as amorphous Li2SO4 at the grain boundaries and intergranular contacts of the primary NMC811 crystallites
The hydroxide precursors precipitated from either sulfates or acetates demonstrate the β-Ni(OH)2-type structure (ICDD #74-2075) for which all diffraction peaks were indexed to a trigonal structure with the P3m1 space group and refined lattice parameters a = 3.121(1), c = 4.612(6) Å (Figure S1a)
Summary
The production of battery-electric (EVs) and hybrid-electric vehicles (HEVs) has intensively grown since they provide ecologically more friendly transportation. The introduction of additional layers consisting of metal oxides [14], fluorides [15], or polymers [16] on the surface of the secondary particles is the most common approach These coating materials are usually poor Li-ion conductors. One of the approaches applied in all-solid-state batteries aimed at solving the conductivity problem is adding at least 20 mol% of amorphous matrixes into cathode materials [17] Despite such modification increasing both electronic and ionic conductivities, this method is expected to decline energy density. Integration of amorphous Li2SO4 into Ni-rich NMC secondary particles, predominantly to the boundaries between the primary particles and their intergranular contacts, increases the secondary agglomerates’ interfacial fracture toughness It suppresses mechanical fracture of the cathode particles during electrochemical cycling. The composite cathode material synthesis does not include additional time- and cost-consuming operational steps, which makes such material attractive for industry needs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
