An epitaxy layer on the LiNi0.8Co0.1Mn0.1O2 cathode significantly suppressed the nickel-ion crossover, which enhanced the structural/electrochemical stability at high temperature.

Electrolyte additives have been explored to attain significant breakthroughs in the long-term cycling performance of lithium-ion batteries (LIBs) without sacrificing energy density; this has been achieved through the development of stable electrode interfacial structures and the elimination of reactive substances. Here we highlight the potential and the challenges raised by studies on electrolyte additives toward addressing the interfacially induced deterioration of high-capacity electrodes with a focus on Ni-rich layered oxides and Si, which are expected to satisfy the growing demands for high-energy-density batteries. We also discuss issues with the design of electrolyte additives for practical viability. A deep understanding of the roles of existing electrolyte additives depending on their functional groups will aid in the design of functional additive moieties capable of building robust interfacial layers, scavenging undesired reactive species, and suppressing the gas generation that causes safety hazards and shortened lifetimes of LIBs.

The layered nickel-rich materials have attracted extensive attention as a promising cathode candidate for high-energy density lithium-ion batteries (LIBs). However, they have been suffering from inherent structural and electrochemical degradation including severe capacity loss at high electrode loading density (>3.0 g cm ) and high temperature cycling (>60 °C). In this study, an effective and viable way of creating an artificial solid-electrolyte interphase (SEI) layer on the cathode surface by a simple, one-step approach is reported. It is found that the initial artificial SEI compounds on the cathode surface can electrochemically grow along grain boundaries by reacting with the by-products during battery cycling. The developed nickel-rich cathode demonstrates exceptional capacity retention and structural integrity under industrial electrode fabricating conditions with the electrode loading level of ≈12 mg cm and density of ≈3.3 g cm . This finding could be a breakthrough for the LIB technology, providing a rational approach for the development of advanced cathode materials.

along the grain boundaries. [12][13][14][15] Consequently, such structural instability causes rapid capacity fading and poor electrochemical performance, which are ascribed to the deteriorated ionic and electronic conduction. To date, many surface treatment and morphology control technologies have been suggested to prevent capacity fading and structure degradation during cycling. [3] For the surface treatment of nickel-based layered cathodes, this concept is considered as a very simple and viable way by introducing additional layers consisting of polymer, [16] metal phosphate, [17,18] metal fluoride, [19,20] metal oxide, [21,22] or core shell [23][24][25] on the surface of the secondary particle clusters. The point that is often overlooked, however, is that these approaches do not fully prevent the fundamental issues related to the grain boundaries among the primary particles. In this context, a novel concept of full concentration-gradient of manganeserich phase with long rod-shaped primary particles was reported and demon strated good structural stability. [26][27][28][29][30] More recently, Cho and co-workers introduced two approaches for the grain boundary coating including the nanoscale surface treatment by cobalt-rich cation mixing layer [31] and spinel-like Li x CoO 2 layer as a glue-nanofiller [32] for highly stable active materials, where an improved structural and thermal stability was achieved by suppressing the phase transition from layered to rock-salt phase of primary particles. However, these kinds of surface treatment methods accompanied a multistep coprecipitation process [29,30] or were carried out after coprecipitation process of active materials by using additional chemicals for surface coatings, [31][32][33] which can cause the increase of the process time and capital cost.Herein, we report a highly stable LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathode with a TM concentration gradient in primary particles and inner pores in secondary particles via a simple, one-step coprecipitation method by exploiting polymeric-beads as a sacrificial template without any surface coating reagents. The prepared sample retains the self-induced TM concentration gradient with reduced nickel oxidation state in the primary particles, which significantly improved the structural stability by suppressing the evolution of microcracks in cathode particles at a high voltage cutoff of 4.45 V and even at a high temperature of 60 °C. Additionally, the internal pores in the secondary particles successfully provided a buffer effect against the volume change of the primary particles.The synthesis process for polystyrene beads (PSBs) incorporated LiNi 0.6 Co 0.2 Mn 0.2 O 2 , denoted as a PSB-NCM, is simple and highly scalable. Briefly, the cathode precursor, PSB-Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 , was synthesized by the coprecipitation To meet the demand of electric vehicles and electrical energy storage systems, lithium-ion batteries with high energy density, high rate capability, and thermal stability have been required. [1][2][3] Among the man...

Despite the advantage of high capacity, the practical use of the silicon anode is still hindered by large volume expansion during the severe pulverization lithiation process, which results in electrical contact loss and rapid capacity fading. Here, a combined electrochemical and computational study on the factor for accommodating volume expansion of silicon-based anodes is shown. 1D silicon-based nanostructures with different internal spaces to explore the effect of spatial ratio of voids and their distribution degree inside the fibers on structural stability are designed. Notably, lotus-root-type silicon nanowires with locally distributed void spaces can improve capacity retention and structural integrity with minimum silicon pulverization during lithium insertion and extraction. The findings of this study indicate that the distribution of buffer spaces, electrochemical surface area, as well as Li diffusion property significantly influence cycle performance and rate capability of the battery, which can be extended to other silicon-based anodes to overcome large volume expansion.