Li+ insertion-induced structure transformation in crystalline electrodes vitally influence the energy density and cycle life of secondary lithium-ion battery. However, the influence mechanism of structure transformation-induced Li+ migration on the electrochemical performance of micro-crystal materials is still unclear and the strategy to profit from such structure transformation remains exploited. Here, an interesting self-optimization of structure evolution during electrochemical cycling in Nb2O5 micro-crystal with rich domain boundaries is demonstrated, which greatly improves the charge transfer property and mechanical strength. The lattice rearrangement activates the Li+ diffusion kinetics and hinders the particle crack, thus enabling a nearly zero-degeneration operation after 8000 cycles. Full cell paired with lithium cobalt oxides displays an exceptionally high capacity of 176mAhg-1 at 8000mAg-1 and excellent long-term durability at 6000mAg-1 with 63% capacity retention over 2000 cycles. Interestingly, a unique fingerprint based on the intensity ratio of two X-ray diffraction peaks is successfully extracted as a measure of Nb2O5 electrochemical performance. The structure self-optimization for fast charge transfer and high mechanical strength exemplifies a new battery electrode design concept and opens up a vast space of strategy to develop high-performance lithium-ion batteries with high energy density and ultra-long cycle life.

The estimation of lithium battery pack is always an essential but troubling issue which has difficulty on considering the inconsistency during state estimation. Herein, an innovative statistical distribution-based pack-integrated model for lithium-ion batteries is proposed and applied for state estimation including state of charge and state of energy. The proposed method highlights the modelling concepts that the terminal voltage of the pack-integrated virtual cell is determined by all cells inside the pack, which takes the advantages of a designed dynamic-weighted terminal voltage according to the voltage distribution inside battery pack. Then, the issue of battery pack modelling and state estimation can be transferred into a virtual single cell and no longer have to consider the inconsistency within battery pack, with the advantages for further extending application from conventional battery modelling method based on single cell. Two kinds of mainstream batteries are experimented for validating, including lithium iron phosphate battery and LiNi0·5Co0·2Mn0·3O2, battery, and both have satisfactory precision, where the maximum error is about 1%–2%, and root mean squared error (RMSE) is eliminated to about 1%. The proposed method is validated with better precision performances on estimating states of battery pack with less calculation and storage, and can be applied both on embedded systems and cloud management platforms.

The ionic conductivity, phase components, and microstructures of LATP depend on its synthesis process. However, their relative importance and their interactions with synthesis process parameters (such as source materials, calcination temperature, and sintering temperature) remain unclear. In this work, different source materials were used to prepare LATP via the solid-state reaction method under different calcination and sintering temperatures, and an analysis via orthogonal experiments and machine learning was used to systematically study the effects of the process parameters. Sintering temperatures had the greatest effect on the total ionic conductivity of LATP pellets, followed by the sources and calcination temperatures. Sources, as the foundational factors, directly determine the composition of a major secondary phase of LATP pellets, which influences the whole process. The calcination temperature had limited impact on the ion conductivity of LATP pellets if pellets were sintered under the optimal temperature. The sintering temperature is the most important factor that influences the ion conductivity by eliminating most secondary phases and altering the microstructure of LATP, including the intergranular contact, grain size, relative densities, etc. This work offers a novel perspective to comprehend the synthesis of solid-state electrolytes beyond LATP.

As an abusive method to trigger thermal runaway (TR), the overcharge method has been widely used to evaluate the safety status of lithium-ion batteries (LIBs). In this study, the combustion characteristics of LIBs were systematically studied by overcharging batteries at different charging rates (C-rates). The results indicated that a high C-rate could cause jet flames with temperatures as high as 1350 °C at a relatively low state of charge. Furthermore, certain maximum heat release rate (HRR) and mass loss rate (MLR) values of 192 kW and 1785 g/s were obtained at 1C, respectively. X-ray photoelectron spectroscopy results for sulfur showed that the valence of sulfur was related to the peak HRR. Moreover, a novel safety evaluation technique denoted as the relative overcharge safety status (OCSS) was presented to highlight the safety status of the overcharging battery. We found that the OCSS at different C-rates presented a linear relationship with the dimensionless time and obtained the safety threshold, safety boundary, and safety level to easily evaluate the TR risk. Therefore, the OCSS method may provide timely, real-time evidence for battery management systems when batteries are overcharged.

Gas production analysis during the thermal runaway (TR) process plays a crucial role in early fire accident detection in electric vehicles. To assess the TR behavior of lithium-ion batteries and perform early warning and risk estimation, gas production and analysis were conducted on LiNixCoyMn1-x-yO2/graphite and LiFePO4/graphite cells under various trigger conditions. The findings indicate that the unique gas signals can provide TR warnings earlier than temperature, voltage, and pressure signals, with an advanced warning time ranging from 16 to 26 min. A new parameter called the thermal runaway degree (TRD) is introduced, which is the product of the molar quantity of gas production and the square root of the maximum temperature during the TR process. TRD is proposed to evaluate the severity of TR. The research reveals that TRD is influenced by the energy density of cells and the trigger conditions of TR. This parameter allows for a quantitative assessment of the safety risk associated with different battery types and the level of harm caused by various abuse conditions. Despite the uncertainties in the TR process, TRD demonstrates good repeatability (maximum relative deviation < 5%) and can be utilized as a characteristic parameter for risk estimation in lithium-ion batteries.

The detrimental growth of lithium dendrites and unstable solid electrolyte interphase (SEI) inhibit the practical application of lithium-metal batteries. Herein, atomically dispersed cobalt coordinate conjugated bipyridine-rich covalent organic framework (sp2 c-COF) is explored as an artificial SEI on the surface of the Li-metal anode to resolve these issues. The single Co atoms confined in the structure of COF enhance the number of active sites and promote electron transfer to theCOF. The synergistic effects of the Co─N coordination and strong electron-withdrawing cyano-group can adsorb the electron from the donor (Co) at a maximum and create an electron-rich environment, hence further regulating the Li+ local coordination environment and achieving uniform Li-nucleation behavior. Furthermore, in situ technology and density functional theory calculations reveal the mechanism of the sp2 c-COF-Co inducing Li uniform deposition and promoting Li+ rapid migration. Based on these advantages, the sp2 c-COF-Co modified Li anode exhibits a low Li-nucleation barrier of 8mV, and excellent cycling stability of 6000h.

Lithium-rich layered oxides, as one of the most potential cathode materials for lithium-ion batteries, still need crucial improvements in mechanical strength and cycle life. Herein, we present an effective strategy to improve the compacted density and cycle stability of Li-rich materials by adding the sintering additive (H3BO3, Li2WO4) for reheating. After reheating with a complex additive of Li2WO4 and H3BO3, the compacted density increased from 3.07 to 3.29, and micromorphology changed from spherical secondary agglomerate to dispersive single crystals with micrometer size. It was found that after reheating with Li2WO4, the sample exhibited a discharge capacity of 241.9 mAh g-1 with an improved ICE of 80.9 %, and cycle life extended to 658 cycles, increased by nearly 250 cycles. This work guides the industrialization of Li-rich cathodes.

With the rapid increase in demand for high-energy-density lithium-ion batteries in electric vehicles, smart homes, electric-powered tools, intelligent transportation, and other markets, high-nickel multi-element materials are considered to be one of the most promising cathode candidates for large-scale industrial applications due to their advantages of high capacity, low cost, and good cycle performance. In response to the competitive pressure of the low-cost lithium iron phosphate battery, high-nickel multi-element cathode materials need to continuously increase their nickel content and reduce their cobalt content or even be cobalt-free and also need to solve a series of problems, such as crystal structure stability, particle microcracks and breakage, cycle life, thermal stability, and safety. In this regard, the research progress of high-nickel multi-element cathode materials in recent years is reviewed and analyzed, and the progress of performance optimization is summarized from the aspects of precursor orientational growth, bulk phase doping, surface coating, interface modification, crystal morphology optimization, composite structure design, etc. Finally, according to the industrialization demand of high-energy-density lithium-ion batteries and the challenges faced by high-nickel multi-element cathode materials, the performance optimization direction of high-nickel multi-element cathode materials in the future is proposed.

The commercial application of Li-rich Mn-based layered oxides (LLOs) is hindered due to their instability of lattice oxygen and dissolution of manganese. Herein, an effective and large-scale production co-precipitation boron-doping strategy was proposed to improve the performance of Li1.15Mn0.53Ni0.22Co0.1O2. We found that the boron introduced in the co-precipitation process will be uniformly distributed in the bulk and the resulting boron-doped Li1.15Mn0.53Ni0.22Co0.1O2 shows excellent electrochemical properties with low doping amount. Multi-dimensional analysis shows that boron doping significantly improves the structural stability of materials. After 1200 cycles at 1C, boron-doped sample can deliver 147 mAhg−1 with an excellent retention of 80.1%, which is much higher than that of the pristine sample of 44% after 700 cycles. Moreover, the discharge voltage decay of the boron-doped samples is only 0.54 mV per cycle (1.39 mV for pristine). It is worth mentioning that the pouch-cell full battery cycle performance of doped samples is also excellent. The doped cathode//graphite shows a superior capacity retention of 83.6% after 500 cycles without gas generation, while the pristine//graphite only hold the 46.6% of initial capacity. The dQ/dV curves and the SEM/EDS of electrode analysis verified higher reversibility of lattice oxygen, less manganese dissolution and more stable microstructure, which greatly improved the cycling life after boron doping.