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Lithium oxalate (Li2C2O4) is an attractive cathode pre-lithiation additive for lithium-ion batteries (LIBs), but its application is hindered by its high decomposition potential (>4.7 V). Due to the liquid–solid synergistic effect of the NaNO2 additive and the LiNi0.83Co0.07Mn0.1O2 (NCM) cathode material, the decomposition efficiency of micro-Li2C2O4 reaches 100% at a low charge cutoff voltage of 4.3 V. Our work boosts the widespread practical application of Li2C2O4 by a simple and promising electrolyte-assisted cathode pre-lithiation strategy. [ABSTRACT FROM AUTHOR]

Na+ doping can selectively stabilize surrounding Li+ by modulating the orientation of the Jahn-Teller effect of Ni3+. These stabilized Li+ ions navigate a prioritized high-speed pathway for Li+ migration, which can significantly enhance the Li+ diffusion kinetics, even in highly delithiated states. [Display omitted] • A novel Li-site Na doping strategy and a mixed molten salt method are proposed. • Na-doped single crystals exhibit excellent rate properties. • A novel mechanism regulating Li+ transport kinetics in NCM materials is revealed. • The NCM-Na material mitigates phase separation and thus reduces structural stresses. Single-crystallization is an effective strategy for enhancing both capacity and stability of Ni-rich LiNi 1-x-y Co x Mn y O 2 (NCM) cathode materials, especially at high cut-off voltages. However, the kinetics limitation of solid-phase Li+ diffusion is a major concern because of the long diffusion path in large single-crystal particles. To address this issue, we synthesize a Na-doped single-crystal LiNi 0.82 Co 0.125 Mn 0.055 O 2 (NCM-Na) cathode material by a facile mixed-molten-salt sintering process. Na+ is revealed to be uniformly doped at the Li+ lattice sites within the entire single-crystal particles. This Na+ doping effectively enhances the dynamics of Li+ transport in the layered oxide phases. The NCM-Na material with 2 at.% Na doping shows a Li+ diffusion coefficient up to more than 8 times higher than pristine NCM. In-situ X-ray diffraction and finite element analysis demonstrate significantly facilitated H1-H2-H3 phase transition in NCM-Na materials, compared with the severe phase separation phenomenon in NCM counterpart, hoisting their rate capacity and structure stability. Thus, the NCM-Na material achieves a superior reversible capacity of 177.7 mAh/g at 5C, and a capacity retention of 94.4 % after 100 cycles at 0.5C at a high cut-off voltage of 4.5 V. By density function theory calculations, we reveal that Na+ doping can selectively stabilize the surrounding Li+ at the second farthest hexagonal vertexes by tuning the orientation of the Jahn-Teller effect of Ni3+. These Li+ ions frame a high-speed pathway for preferential Li+ diffusion, which promotes the Li+ diffusion kinetics even in highly delithiated states. Our findings provide insights into the Na+ doping mechanism and present a low-cost, highly efficient, and scalable method to enhance the performance of single-crystal Ni-rich NCM materials. [ABSTRACT FROM AUTHOR]

Ni‐rich Li[NixCoyMn1−x−y]O2 (x ≥ 0.8) layered oxides are the most promising cathode materials for lithium‐ion batteries due to their high reversible capacity of over 200 mAh g−1. Unfortunately, the anisotropic properties associated with the α‐NaFeO2 structured crystal grains result in poor rate capability and insufficient cycle life. To address these issues, a micrometer‐sized Ni‐rich LiNi0.8Co0.1Mn0.1O2 secondary cathode material consisting of radially aligned single‐crystal primary particles is proposed and synthesized. Concomitant with this unique crystallographic texture, all the exposed surfaces are active {010} facets, and 3D Li+ ion diffusion channels penetrate straightforwardly from surface to center, remarkably improving the Li+ diffusion coefficient. Moreover, coordinated charge–discharge volume change upon cycling is achieved by the consistent crystal orientation, significantly alleviating the volume‐change‐induced intergrain stress. Accordingly, this material delivers superior reversible capacity (203.4 mAh g−1 at 3.0–4.3 V) and rate capability (152.7 mAh g−1 at a current density of 1000 mA g−1). Further, this structure demonstrates excellent cycling stability without any degradation after 300 cycles. The anisotropic morphology modulation provides a simple, efficient, and scalable way to boost the performance and applicability of Ni‐rich layered oxide cathode materials. [ABSTRACT FROM AUTHOR]

• A NaNO 2 -assisted strategy is proposed for cathode prelithiation with Li 2 O 2. • Synergistic effect between the NaNO 2 and cathode is revealed. • The decomposition percentage of Li 2 O 2 is high up to 96.7% at 4.4 V. • For 1 wt% of Li 2 O 2 additive, 14.85 mAh g−1 capacity could be supplied. • NaNO 2 helps to form solid electrolyte interphase rich in Li 3 N and LiN x O y. Silicon based anodes are the most attractive candidates for high energy density lithium-ion batteries (LIBs), but their practical applications are hindered by the large initial lithium loss. Cathode prelithiation is an effective method to mitigate the active lithium loss in silicon-based LIBs. However, a cathode prelithiation method enabling suitable cutoff voltage and less residues still remains challenging. Herein, we demonstrate that soluble additive NaNO 2 in carbonate-based electrolyte could efficiently reduce the decomposition voltage of Li 2 O 2 to as low as 4.3 V. The liquid–solid synergistic effect of NaNO 2 additive and LiNi 0.83 Co 0.07 Mn 0.1 O 2 (NCM) cathode on the Li 2 O 2 decomposition is revealed, which enables the highly efficient cathode prelithiation with remarkable Li 2 O 2 decomposition efficiency of 96.7% at the acceptable cutoff voltage 4.4 V. For the addition for 1 wt% Li 2 O 2 , a capacity of 14.85 mAh/g could be supplied in the first charge. Besides, NaNO 2 could reduce the active lithium loss during the following cycles for its irreversibly decomposing into Li 3 N and LiN x O y on the anode surface. The full cell assembled with NCM(Li 2 O 2) cathode and silicon-graphite (Si-G) anode delivers 17.3% higher initial specific capacity (218.6 mAh/g) than that without Li 2 O 2 (186.4 mAh/g) at the charge cutoff voltage of 4.4 V. This work provides a novel electrolyte-assisted cathode prelithiation strategy to compensate the initial active lithium loss, which is highly compatible with the current battery fabrication process. [ABSTRACT FROM AUTHOR]