The Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode has attracted great interest owing to its low cost, high capacity, and energy density. Nevertheless, rapid capacity fading is a critical problem because of direct contact of NCM811 with electrolytes and hence restrains its wide applications. To prevent the direct contact, the surface inert layer coating becomes a feasible strategy to tackle this problem. However, to achieve a homogeneous surface coating is very challenging. Considering the bonding effect between NCM811, polyvinylpyrrolidone (PVP), and polyaniline (PANI), in this work, we use PVP as an inductive agent to controllably coat a uniform conductive PANI layer on NCM811 (NCM811@PANI–PVP). The coated PANI layer not only serves as a rapid channel for electron conduction, but also prohibits direct contact of the electrode with the electrolyte to effectively hinder side reaction. NCM811@PANI–PVP thus exhibits excellent cyclability (88.7% after 100 cycles at 200 mA g–1) and great rate performance (152 mA h g–1 at 1000 mA g–1). In situ X-ray diffraction and in situ Raman are performed to investigate the charge–discharge mechanism and the cyclability of NCM811@PANI–PVP upon electrochemical reaction. This surfactant-modulated surface uniform coating strategy offers a new modification approach to stabilize Ni-rich cathode materials for lithium-ion batteries.

Carbon materials are most promising candidates for potassium-ion battery (PIB) anodes because of their high electrical conductivities, rational potassium storage capabilities, and low costs. However, the large volume change during the K-ion insertion/extraction and the sluggish kinetics of K-ion diffusion inhibit the development of carbon-based materials for PIBs. Here, under the guidance of density functional theory, N/P-codoped ultrafine (≤20 nm) carbon nanoparticles (NP-CNPs) with an expanded interlayer distance, improved electrical conductivity, shortened diffusion distance of K ions, and promoted adsorption capability toward K ions are synthesized through a facile solvent-free method as a high-performance anode material for PIBs. The NP-CNPs show a high capacity of 270 mA h g–1 at 0.2 A g–1, a remarkable rate capability of 157 mA h g–1 at an extremely high rate of 5.0 A g–1, and an ultralong cycle life with a high capacity of 190 mA h g–1 and a retention of 86.4% at 1.0 A g–1 after 4000 cycles. The potassium storage mechanism and low volume expansion for NP-CNPs are revealed through cyclic voltammetry, in situ Raman, and ex situ XRD. This work paves a new way to design and fabricate carbon-based nanostructures with high reversible capacity, great rate capability, and stable long-term performance.

Lithium-rich layered oxide cathodes have the advantage of high energy density. However, the continuous capacity fading and voltage hysteresis have largely restricted their practical application. In this work, we intensively...

The practical application of LiCoO2 at 4.6 V suffers from the devastating H1-3 metastable phase transition, severe interfacial side reactions due to aggressive oxygen species and cobalt loss, as well...