Building a Self‐Adaptive Protective Layer on Ni‐Rich Layered Cathodes to Enhance the Cycle Stability of Lithium‐Ion Batteries

Abstract

Layered Ni‐rich lithium transition metal oxides are promising battery cathodes due to their high specific capacity, but their poor cycling stability due to intergranular cracks in secondary particles restricts their practical applications. Surface engineering is an effective strategy for improving a cathode's cycling stability, but most reported surface coatings cannot adapt to the dynamic volume changes of cathodes. Herein, a self‐adaptive polymer (polyrotaxane‐co‐poly(acrylic acid)) interfacial layer is built on LiNi0.6Co0.2Mn0.2O2. The polymer layer with a slide‐ring structure exhibits high toughness and can withstand the stress caused by particle volume changes, which can prevent the cracking of particles. In addition, the slide‐ring polymer acts as a physicochemical barrier that suppresses surface side reactions and alleviates the dissolution of transition metallic ions, which ensures stable cycling performance. Thus, the as‐prepared cathode shows significantly improved long‐term cycling stability in situations in which cracks may easily occur, especially under high‐rate, high‐voltage, and high‐temperature conditions.

Enabling Aqueous Processing of Ni‐Rich Layered Oxide Cathode Materials by Addition of Lithium Sulfate

“…[19] It is worth to mention that coatings, which can be applied without an additional annealing step, are able to reduce the production cost of the cathode and the overall manufacturing time. [20] It is expected that the sulfate anion (SO 4 2À ) reacts similarly to PO 4 3À , leading to the formation of a protective surface film; [21,22] however, such a study combined with aqueous processing has not been reported so far. Besides "direct" pH modification, the addition of Li salts [e. g., lithium bis(trifluoromethanesulfonyl)imide; LiTFSI] has proven to mitigate the pH rise and the Li loss upon electrode processing, therefore, for example, enabling aqueous processing of the high-voltage spinel cathode LiNi 0.5 Mn 1.5 O 4 .…”

A eutectic electrolyte for an ultralong-lived Zn//V2O5cell: anin situgenerated gradient solid-electrolyte interphase

“…1–4 Currently, lithium-ion batteries have a high energy density and voltage platform and are extensively used. 5–7 However, their large-scale deployment is limited by the high cost and low abundance of lithium, as well as safety issues resulting from its reactivity with flammable organic electrolytes. 8–10 To address this, alternative metals with sufficient reserve and low cost such as Na, K, Al, Mg, Zn, and Ca have been explored.…”

Micro- and nano-structural design strategies towards polycrystalline nickel-rich layered cathode materials

“…The introduction of a small quantity of titanium, 37 fluorine, 38 stibium, 39 magnesium, 40 boron, 41 strontium, 27 niobium 42 and aluminium 43 as substitutes for transition metal sites can not only mitigate the extent of unit cell volumetric change and preserve the structural integrity in the high charge state, but also balance electrostatic repulsion and regulate the cation mixing degree by providing charge compensation. Surface coating such as oxides, 44–46 fluorides/phosphates 5,47,48 and organic polymers 49,50 can act as stable buffer layers to physically suppress side reactions by preventing the NRLOs from being directly exposed to the electrolyte. Despite the efficacy of atomic doping and surface coating, these methods merely delay the onset of the degradation process of the NRLOs.…”