Dual Substitution Strategy in Co-Free Layered Cathode Materials for Superior Lithium Ion Batteries

Abstract

A dual substitution strategy is introduced to Co-free layered material LiNi0.5Mn0.5O2 by partially replacing Li and Ni with Na and Al, respectively, to achieve a superior cathode material for lithium ion batteries. Na+ ion functions as a “pillar” and a “ cationic barrier” in the lithium layer while Al3+ ion plays an auxiliary role in stabilizing structure and lattice oxygen to improve the electrochemical performance and safety. The stability of lattice oxygen comes from the binding energy between the Ni and O, which is larger due to higher valences of Ni ions, along with a stronger Al–O bond in the crystal structure and the “cationic barrier” effect of Na+ ion at the high-charge. The more stable lattice oxygen reduces the cation disorder in cycling, and Na+ in the Li layer squeezes the pathway of the transition metal from the LiM2 (M = metal) layer to the Li layer, stabilizing the layered crystal structure by inhibiting the electrochemical-driven cation disorder. Moreover, the cathode with Na–Al dual-substitution displays a smaller volume change, yielding a more stable structure. This study unravels the influence of Na–Al dual-substitution on the discharge capacity, midpoint potential, and cyclic stability of Co-free layered cathode materials, which is crucial for the development of lithium ion batteries.

Metal-Complex-Assisted Synthesis of SnSe Nanorods for Lithium-Ion-Battery Anodes

“…21,22 Compared with the SnSe nanoparticles (Figure S5a), the reduction and oxidation peaks of the SnSe nanorods largely overlap in the following two circles, indicating the good electrochemical reversibility of the SnSe nanorods electrode. 31,57 Figure 5b displays the first five discharge/charge curves of SnSe nanorods at 100 mA g −1 . The charge/discharge specific capacities of the first cycle are 683.6 and 1307.2 mAh g −1 , and the corresponding initial CE is 52.3%, higher than 27.6% of SnSe nanoparticles (Figure S5b).…”

“…Figure a shows the CV curves of the SnSe nanorod under a scanning range of 0.05–3.0 V. During the first cathodic scan, the reduction peak centered at 1.17 V corresponds to the conversion of SnSe to Sn and Li 2 Se, and it is also related to formation of the solid electrolyte interface (SEI) film. − However, the first cathodic curve is different from the following cathodic curves because of the structural changes and the SEI films resulting in irreversible reactions. , The subsequent reduction peak centered at 0.11 V is associated with the alloying reactions between Sn and Li . During the first anodic scan, the broad peak centered at 0.60 V is assigned to the dealloying of Li x Sn, and the oxidation peak centered at 1.79 V is ascribed to the oxidation of Sn to Sn 2+ . , Compared with the SnSe nanoparticles (Figure S5a), the reduction and oxidation peaks of the SnSe nanorods largely overlap in the following two circles, indicating the good electrochemical reversibility of the SnSe nanorods electrode. , …”

Low-Cost Mn-Based Cathode Materials for Lithium-Ion Batteries

“…In addition to single-element doping, the double-element co-doping is applied in LiNi 0.5 Mn 0.5 O 2 , which has shown better improvement than single-element doping. Jia et al [40] realized a Na-Al dual-doped LiNi 0.5 Mn 0.5 O 2 material, improving the reversible capacity, cycling stability, and the stability of discharge midpoint potential (Figure 2d). Na + successfully entered into the lithium layer and played a "pillar" role to promote the structural stability, as opposed to hindering the diffusion of Li + .…”

High Nickel and No Cobalt─The Pursuit of Next-Generation Layered Oxide Cathodes

“…Eliminating Co and increasing Ni in layered NCM cathodes conforms to the future demands of LIBs and has become the preferred development strategy of battery manufacturers . LiNiO 2 (LNO) has thus re-emerged in the public consciousness as a promising starting material for Co-free cathodes, despite the fact that it was long overlooked because of numerous inherent issues such as off-stoichiometry, Li/Ni exchange, Ni 3+ instability, poor thermal stability, low Coulombic efficiency, multiple phase transitions, and fast capacity fading upon cycling. , Foreign heteroatom doping, such as Co, Mg, Al, Mn, and others, has generally been considered a good option for stabilizing the layered structure and enhancing the electrochemical reversibility to alleviate these issues of LNO. − In addition, Co as the most successful substitution can be incorporated into LNO at high enough levels. For the aim of eliminating Co, it is very necessary to clarify its roles in the Ni-rich cathodes.…”