Thermal Stability and Outgassing Behaviors of High-nickel Cathodes in Lithium-ion Batteries

Manipulated Fluoro-Ether Derived Nucleophilic Decomposition Products for Mitigating Polarization-Induced Capacity Loss in Li-Rich Layered Cathode

Electrolyte engineering is a fascinating choice to improve the performance of Li-rich layered oxide cathodes (LRLO) for high-energy lithium-ion batteries. However, many existing electrolyte designs and adjustment principles tend to overlook the unique challenges posed by LRLO, particularly the nucleophilic attack. Here, we introduce an electrolyte modification by locally replacing carbonate solvents in traditional electrolytes with a fluoro-ether. By benefit of the decomposition of fluoro-ether under nucleophilic O-related attacks, which delivers an excellent passivation layer with LiF and polymers, possessing rigidity and flexibility on the LRLO surface. More importantly, the fluoro-ether acts as "sutures", ensuring the integrity and stability of both interfacial and bulk structures, which contributed to suppressing severe polarization and enhancing the cycling capacity retention from 39 % to 78 % after 300 cycles for the 4.8 V-class LRLO. This key electrolyte strategy with comprehensive analysis, provides new insights into addressing nucleophilic challenge for high-energy anionic redox related cathode systems.

Electrolyte Engineering Toward High Performance High Nickel (Ni ≥ 80%) Lithium-Ion Batteries

High nickel (Ni ≥ 80%) lithium-ion batteries (LIBs) with high specific energy are one of the most important technical routes to resolve the growing endurance anxieties. However, because of their extremely aggressive chemistries, high-Ni (Ni ≥ 80%) LIBs suffer from poor cycle life and safety performance, which hinder their large-scale commercial applications. Among varied strategies, electrolyte engineering is very powerful to simultaneously enhance the cycle life and safety of high-Ni (Ni ≥ 80%) LIBs. In this review, the pivotal challenges faced by high-Ni oxide cathodes and conventional LiPF6 -carbonate-based electrolytes are comprehensively summarized. Then, the functional additives design guidelines for LiPF6 -carbonate -based electrolytes and the design principles of high voltage resistance/high safety novel electrolytes are systematically elaborated to resolve these pivotal challenges. Moreover, the proposed thermal runaway mechanisms of high-Ni (Ni ≥ 80%) LIBs are also reviewed to provide useful perspectives for the design of high-safety electrolytes. Finally, the potential research directions of electrolyte engineering toward high-performance high-Ni (Ni ≥ 80%) LIBs are provided. This review will have an important impact on electrolyte innovation as well as the commercial evolution of high-Ni (Ni ≥ 80%) LIBs, and also will be significant to breakthrough the energy density ceiling of LIBs.

Progress, Challenge, and Prospect of LiMnO2 : An Adventure toward High-Energy and Low-Cost Li-Ion Batteries

Lithium manganese oxides are considered as promising cathodes for lithium-ion batteries due to their low cost and available resources. Layered LiMnO2 with orthorhombic or monoclinic structure has attracted tremendous interest thanks to its ultrahigh theoretical capacity (285 mAh g-1 ) that almost doubles that of commercialized spinel LiMn2 O4 (148 mAh g-1 ). However, LiMnO2 undergoes phase transition to spinel upon cycling cause by the Jahn-Teller effect of the high-spin Mn3+ . In addition, soluble Mn2+ generates from the disproportionation of Mn3+ and oxygen release during electrochemical processes may cause poor cycle performance. To address the critical issues, tremendous efforts have been made. This paper provides a general review of layered LiMnO2 materials including their crystal structures, synthesis methods, structural/elemental modifications, and electrochemical performance. In brief, first the crystal structures of LiMnO2 and synthetic methods have been summarized. Subsequently, modification strategies for improving electrochemical performance are comprehensively reviewed, including element doping to suppress its phase transition, surface coating to resist manganese dissolution into the electrolyte and impede surface reactions, designing LiMnO2 composites to improve electronic conductivity and Li+ diffusion, and finding compatible electrolytes to enhance safety. At last, future efforts on the research frontier and practical application of LiMnO2 have been discussed.

Implanting Transition Metal into Li2 O-Based Cathode Prelithiation Agent for High-Energy-Density and Long-Life Li-Ion Batteries

Compensating the irreversible loss of limited active lithium (Li) is essentially important for improving the energy-density and cycle-life of practical Li-ion battery full-cell, especially after employing high-capacity but low initial coulombic efficiency anode candidates. Introducing prelithiation agent can provide additional Li source for such compensation. Herein, we precisely implant trace Co (extracted from transition metal oxide) into the Li site of Li2 O, obtaining (Li0.66 Co0.11 □0.23 )2 O (CLO) cathode prelithiation agent. The synergistic formation of Li vacancies and Co-derived catalysis efficiently enhance the inherent conductivity and weaken the Li-O interaction of Li2 O, which facilitates its anionic oxidation to peroxo/superoxo species and gaseous O2 , achieving 1642.7 mAh/g~Li2O prelithiation capacity (≈980 mAh/g for prelithiation agent). Coupled 6.5 wt % CLO-based prelithiation agent with LiCoO2 cathode, substantial additional Li source stored within CLO is efficiently released to compensate the Li consumption on the SiO/C anode, achieving 270 Wh/kg pouch-type full-cell with 92 % capacity retention after 1000 cycles.

Irreparable Interphase Chemistry Degradation Induced by Temperature Pulse in Lithium-Ion Batteries

While it is widely recognized that the operating temperature significantly affects the energy density and cycle life of lithium-ion batteries, the consequence of electrode-electrolyte interphase chemistry to sudden environmental temperature changes remains inadequately understood. Here, we systematically investigate the effects of a temperature pulse (T pulse) on the electrochemical performance of LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) pouch full cells. By utilizing advanced characterization tools, such as time-of-flight secondary-ion mass spectrometry, we reveal that the T pulse can lead to an irreversible degradation of cathode-electrolyte interphase chemistry and architecture. Despite negligible immediate impacts on the solid-electrolyte interphase (SEI) on graphite anode, aggregated cathode-to-anode chemical crossover gradually degrades the SEI by catalyzing electrolyte reduction decomposition and inducing metallic dead Li formation because of insufficient cathode passivation after the T pulse. Consequently, pouch cells subjected to the T pulse show an inferior cycle stability to those free of the T pulse. This work unveils the effects of sudden temperature changes on the interphase chemistry and cell performance, emphasizing the importance of a proper temperature management in assessing performance.

A foldable self-healing rocking chair zinc-ion battery using a three-dimensional zinc metal-free anode

We developed H2Ti5O11·xH2O on carbon cloth (HTO·xH2O/CC) as a binder-free Zn metal-free anode. This 'rocking chair' battery incorporated a ZnMn2O4/CC cathode, HTO·xH2O/CC anode, and a polyacrylamide-based electrolyte, and exhibited satisfactory flexibility and self-healing. It displayed recoverable capacities after four repetitions of cutting and healing, indicating a potential using as a foldable and wearable battery.