In Situ Co-modification Strategy for Achieving High-Capacity and Durable Ni-Rich Cathodes for High-Temperature Li-Ion Batteries

Abstract

Operating Li-ion batteries in a harsh environment will greatly degrade the cyclic performance and safety of Ni-rich layered cathodes, which challenges the current modification approaches to form a more stable interface with the electrolyte and a robust crystal structure. Herein, we demonstrate the surface engineering enabling V-doped and ZrV 2 O 7 -coated Ni-rich layered cathodes (V-NCM@ZVO), where stoichiometric ZVO generates on the surface of oxides and tailorable V subsequently diffuses into the bulk phase during high-temperature lithiation. The introduction of high-energy V−O bonds vastly refrains the lattice oxygen escape, and meantime, ionic conductive and electrochemically inert ZVO ensures a robust interphase on the Ni-rich cathode, greatly enhancing the thermal stability. At 55 °C, the modified cathode displays a high reversible capacity of 220.3 mAh g −1 at 0.2 C and 183.0 mAh g −1 at 10 C. More impressively, the assembled V-NCM@ZVO//graphite pouch-type cell exhibits a capacity retention of 90.2% at 1 C after 400 cycles at 55 °C. This work exhibits a feasible modification strategy to strengthen the surface and crystal stability in parallel of Ni-rich cathodes to meet high-temperature Li-ion batteries.

Building Negative‐Thermal‐Expansion Protective Layers on the Grain Boundary of Ni‐rich Cathodes Enables Safe and Durable High Voltage Lithium‐Ion Batteries

“…Compared to the pristine NCM811, 1.25%ZVO-NCM811 shows not only a strong V 2p signal (Figure 1f, not present in the pristine NCM811) but also a strong Zr 3d signal (Figure 1g). [34] However, the Ni 2p, Co 2p, and Mn 2p signals (relative to the strong signals in the original NCM811 in Figure 1e and Figure S10a-c, Supporting Information). [21,36] As XPS is a surface-sensitive technique, the absence of Ni, Co, and Mn signals indicates that the ZVO coating has a thicker and more complete coverage on the surface of the NCM811 particles (hence the XPS signal is mainly contributed by the coating), in addition to a lower level of residual lithium than the NCM811 material (Figure S10d,e, Supporting Information).…”

“…[18] LiNi 0.83 Co 0.11 Mn 0.06 O 2 material coating and doping modification elevated the phase transition temperature, where the temperature of the layer to spinel phase was increased by 20 °C, and the complete transition from spinel to rock salt phase was 600 °C. [34] Therefore, building a protective layer for both the primary and secondary particles of cathode materials using negative thermal expansion NTE materials is expected to be capable of mitigating phase transitions and mechanical stresses and meanwhile solving the thermal-runaway problem.…”

The role of niobium in layered oxide cathodes for conventional lithium-ion and solid-state batteries

“…21 These characteristics translate to an observed reduction in degradation and improvements to lithium diffusion kinetics when Nb 5+ is employed as a dopant. Other element dopants with comparable ionic radius and higher valence than the TMs in LTMOs, such as V 5+ , 22–24 Ta 5+ , 25–27 Mo 6+ , 28–30 and W 6+ , 31–33 have also been reported to exhibit similar improvements. Another work has outlined the impact of these and various other dopants and coating materials on Ni-rich CAMs.…”

Surface Engineering of Ni-Rich Cathodes Enables Homogeneous Doping of High-Valence Mo Ions for Li-Ion Batteries

“…A successful method for improving stability and mitigating capacity degradation is metal cation doping. − Recent studies have highlighted the potential of doping high-valence elements, such as Nb, , Sb, Ta, and Mo, to induce a radial arrangement of primary particles by regulating crystal surface energy. Consequently, the doped cathode exhibits a conversion of uneven strain distribution into a uniform circumferential strain, effectively inhibiting local stress concentration, dissipating mechanical strain, and preventing intergranular cracks. − Moreover, the stronger metal–oxygen (M–O) bond resulting from the doping process aids in alleviating Li/Ni cation mixing and the escape of lattice oxygen, leading to Ni-rich oxides with enhanced cycle durability and thermal stability. ,, Mo has emerged as one of the most efficient agents among those that have been reported for refining primary particles over a broad range of calcination temperature . However, the majority of reported Mo-doped Ni-rich oxides have been synthesized by mixing the precursor with molybdenum oxides followed by the calcination process, which could potentially lead to an accumulation of Mo 6+ ions along the interparticle boundaries or a formation of Li 2 MoO 4 coating layer and result in low doping efficiency. ,− …”

“…27−29 Moreover, the stronger metal− oxygen (M−O) bond resulting from the doping process aids in alleviating Li/Ni cation mixing and the escape of lattice oxygen, leading to Ni-rich oxides with enhanced cycle durability and thermal stability. 23,30,31 Mo has emerged as one of the most efficient agents among those that have been reported for refining primary particles over a broad range of calcination temperature. 26 However, the majority of reported Mo-doped Ni-rich oxides have been synthesized by mixing the precursor with molybdenum oxides followed by the calcination process, which could potentially lead to an accumulation of Mo 6+ ions along the interparticle boundaries or a formation of Li 2 MoO 4 coating layer and result in low doping efficiency.…”