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Advancement in energy storage technologies is closely related to social development. However, a significant conflict has arisen between the explosive growth in battery demand and resource availability. Facing the upcoming large-scale disposal problem of spent lithium-ion batteries (LIBs), their recycling technology development has become key. Emerging direct recycling has attracted widespread attention in recent years because it aims to 'repair' the battery materials, rather than break them down and extract valuable products from their components. To achieve this goal, a profound understanding of the failure mechanisms of spent LIB electrode materials is essential. This review summarizes the failure mechanisms of LIB cathode and anode materials and the direct recycling strategies developed. We systematically explore the correlation between the failure mechanism and the required repair process to achieve efficient and even upcycling of spent LIB electrode materials. Furthermore, we systematically introduce advanced in situ characterization techniques that can be utilized for investigating direct recycling processes. We then compare different direct recycling strategies, focussing on their respective advantages and disadvantages and their applicability to different materials. It is our belief that this review will offer valuable guidelines for the design and selection of LIB direct recycling methods in future endeavors. Finally, the opportunities and challenges for the future of battery direct recycling technology are discussed, paving the way for its further development. [ABSTRACT FROM AUTHOR]

The structure instability issues of the highly delithiated LiCoO2 have significantly hindered its high‐voltage applications (≥4.55 V vs Li/Li+). Herein, for the first time, multiple modifications of Li0.9Mg0.05CoO2 (L0.9M0.05CO) via a simple one‐step sintering synthesis are reported. A combination of the bulk Li/Co antisites, a Mg‐pillar enriched surface, and a thin MgO coating layer is achieved to maintain both the bulk and surface structural stability of L0.9M0.05CO upon cycling at an upper cut‐off voltage of 4.6 V. The bulk Li/Co antisites are discovered to enhance the H1‐3 phase evolution reversibility, the Mg pillars that substitute the Li sites effectively reinforces the surface structure, and the thin MgO coating layer can effectively prevent the cathode from severe side reactions. Benefiting from the reduced but reversible H1‐3 phase transition and the reinforced surface structure, L0.9M0.05CO shows an excellent cycle stability. This work provides a new structure modulation route for developing high‐voltage LiCoO2 cathodes. [ABSTRACT FROM AUTHOR]

Compressors are important components in various power systems in the field of energy and power. In practical applications, compressors often operate under non-design conditions. Therefore, accurate calculation on performance under various operating conditions is of great significance for the development and application of certain power systems equipped with compressors. To calculate and predict the performance of a compressor under all operating conditions through limited data, the interpolation method was combined with a support vector machine (SVM). Based on the known data points of compressor design conditions, the interpolation method was adopted to obtain training samples of the SVM. In the calculation process, preliminary screening was conducted on the kernel functions of the SVM. Two interpolation methods, including linear interpolation and cubic spline interpolation, were used to obtain sample data. In the subsequent training process of the SVM, the genetic algorithm (GA) was used to optimize its parameters. After training, the available data were compared with the predicted data of the SVM. The results show that the SVM uses the Gaussian kernel function to achieve the highest prediction accuracy. The prediction accuracy of the SVM trained with the data obtained from linear interpolation was higher than that of cubic spline interpolation. Compared with the back propagation neural network optimized by the genetic algorithm (GA-BPNN), the genetic algorithm optimization of extreme learning machine neural network (GA-ELMNN), and the genetic algorithm optimization of generalized regression neural network (GA-GRNN), the support vector machine optimized by the genetic algorithm (GA-SVM) has a better generalization, and GA-SVM is more accurate in predicting boundary data than the GA-BPNN. In addition, reducing the number of original data points still enables the GA-SVM to maintain a high level of predictive accuracy. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion batteries. The Li+ diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock‐salt phase was coherently constructed at the surface of LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−1 at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high‐rate cathode materials by tuning the surface electron transport property. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion batteries. The Li+ diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock‐salt phase was coherently constructed at the surface of LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−1 at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high‐rate cathode materials by tuning the surface electron transport property. [ABSTRACT FROM AUTHOR]

The application of direct injection (DI) technology can effectively improve the atomization effect of heavy fuel to reduce the fuel loss of heavy fuel engines (HFE). The fuel spray characteristics directly affect the combustion performance of the engine. To investigate the atomization process and evaporation characteristics of heavy fuel in-cylinder for an air-assisted direct injection (AADI) engine, a simulation calculation model of AADI HFE was established with the use of a computational fluid dynamics tool. The air-assisted injector model and the one-dimensional performance calculation model were verified by test data. The influences of injection timing and injection pressure on the spray characteristics and mixture formation in the engine cylinder were discussed. The results show that the mixture concentration distribution is uniform after the injection timing is advanced, and the mass fraction of the fuel evaporation increases. The earlier injection timing can provide the fuel with sufficient time to evaporate, while the later injection timing will result in increasing the Sauter mean diameter (SMD) of the fuel droplets, and the unevaporated heavy fuel in the combustion chamber tends to become concentrated. With the increase in air injection pressure, the distribution of the mixed gas in the cylinder becomes uniform, and the SMD of the fuel droplets in the cylinder decreases. When the injection pressure is 0.65 MPa and 0.75 MPa, the difference between the SMD of the fuel droplets in-cylinder decreases, and a favorable fuel atomization effect can be maintained. [ABSTRACT FROM AUTHOR]

To effectively enhance the thermal security of the Li-ion battery packs used in the electric vehicle industry, novel cooling systems equipped with serpentine channels are established. Then, the heat generation model is established and verified experimentally. In this research study, the structure of the cooling channel, the coolant velocity, the coolant temperature, and the coolant flow direction are considered to be the influencing factors. The results demonstrate that, by adopting the serpentine cooling channel, a better thermal conductivity can be obtained, and the type-B cooling system possesses a more reasonable structure. For different types of liquid cooling systems, the coolant temperature has a small influence on the temperature nephogram; however, for the same type of system, the coolant temperature strongly influences the temperature distribution. Similarly, the temperature difference is only related to the type of cooling system, with ∼6.09 and 5.53 K obtained for the type-A and type-B cooling systems, respectively. Furthermore, allowing the coolant in the serpentine cooling channels to flow in opposite directions can lower the value of the maximum temperature and temperature difference. [ABSTRACT FROM AUTHOR]

In the process of upgrading energy storage structures, sodium‐ion batteries (SIBs) are regarded as the most promising candidates for large‐scale grid storage systems. However, the difficulty in further improving their specific capacity and lifespan has become a major obstacle to promoting extensive application. Herein, by optimizing synthesis conditions, a biphasic‐Na2/3Ni1/3Mn2/3O2 cathode that exhibits an ultrahigh capacity of ≈200 mAh g‐1 without the involvement of anion redox reactions is successfully synthesized. Nevertheless, there is significant electrochemical performance degradation because of failure at the cathode‐electrolyte interface as revealed by comprehensive analyses. Further in‐depth research proves that the surface side reactions that occur at high operating voltages and the transition metal dissolution that occurs in low voltage are the root causes of electrode surface failure. Therefore, the metal oxide atomic layer deposition (ALD) protective layer is deliberately chosen to suppress such failures. The coating effectively blocks corrosion of the cathode material by the electrolyte and successfully anchors the transition metal ions on the particle surface. As a result, the cycle stability and rate performance of the electrode are improved considerably. This surface engineering strategy could provide concepts with broad applicability for suppressing the failure of sodium layered cathodes. [ABSTRACT FROM AUTHOR]

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In our work, the novel sparsely and compactly MoO3 nanoflowers were synthesized by a hydrothermal method assisted with polyvinyl pyrrolidone (PVP) and without any template, respectively. Through X-ray diffraction and scanning electron microscopy, we can confirm that we have prepared high purity MoO3 and can observe that both nanoflowers are formed by self-assembly of thin nanosheets. They have similar morphology, size and formation mechanism, but differ from pore size and quantity. Because of the above differences, sparsely MoO3 nanoflowers have a larger specific surface area and form more enclosed micro-reaction chambers that make it difficult for ethanol to escape. Allowing gas molecules to be more widely distributed among the sparsely sample surface and obtained fully reaction time. Thus, the gas sensor based on compactly MoO3 nanoflowers exhibits a better response and recovery characteristic. [ABSTRACT FROM AUTHOR]

A high-energy multispark ignition system with a single discharge capacitor was designed and developed. The ignition system was verified to be capable of releasing high ignition energy. The cold start and partial-load test at 6 °C ambient temperature were conducted on a two-stroke spark ignition heavy fuel engine with air-assisted direct injection. The results showed that compared to the original magnetoignition system, applying the 5-times multispark ignition approach with the new ignition system is able to successfully solve the cold start problem of the heavy fuel engine. Under the partial-load condition, increasing the number of ignitions enhances combustion in the cylinder. Four-times ignition is better than 2-times ignition with the ignition timing angle between 10° and 20°CA BTDC, improving the power output, fuel economy, and HC/CO emissions performance. The effects of multispark ignition gradually become small with the ignition timing angle advanced to 30°CA BTDC. [ABSTRACT FROM PUBLISHER]

• The temperature distribution of a Li-ion battery pack was investigated and the model was verified by independent test. • The square cooling channel can lower the highest temperature more effectively than the circular cooling channel, but results in a slight increase in the temperature dispersion. • As the aspect ratio increases, the temperature dispersion of the battery pack initially decreases and then increases. • In this paper, the most balanced temperature distribution domain is located near the No. 5 single lithium-ion battery. In this article, we studied liquid cooling systems with different channels, carried out simulations of lithium-ion battery pack thermal dissipation, and obtained the thermal distribution. According to the results shown in the study, the number of channels is inversely proportional to the highest temperature and the temperature dispersion. A liquid cooling system with a square channel can achieve a lower highest temperature than that of a liquid cooling section with a circular channel. Simultaneously, the highest temperature is also negatively correlated with the rectangular channel aspect ratio. In addition, as the aspect ratio increases, the temperature dispersion of the battery pack initially decreases and then increases. Furthermore, from the entrance, along the direction of coolant flow, the temperature dispersion of a single lithium-ion battery will initially increase and then gradually decrease, which indicates that the No. 5 lithium-ion battery is the most balanced module in the battery pack. [ABSTRACT FROM AUTHOR]

The structure instability issues of the highly delithiated LiCoO2 have significantly hindered its high‐voltage applications (≥4.55 V vs Li/Li+). Herein, for the first time, multiple modifications of Li0.9Mg0.05CoO2 (L0.9M0.05CO) via a simple one‐step sintering synthesis are reported. A combination of the bulk Li/Co antisites, a Mg‐pillar enriched surface, and a thin MgO coating layer is achieved to maintain both the bulk and surface structural stability of L0.9M0.05CO upon cycling at an upper cut‐off voltage of 4.6 V. The bulk Li/Co antisites are discovered to enhance the H1‐3 phase evolution reversibility, the Mg pillars that substitute the Li sites effectively reinforces the surface structure, and the thin MgO coating layer can effectively prevent the cathode from severe side reactions. Benefiting from the reduced but reversible H1‐3 phase transition and the reinforced surface structure, L0.9M0.05CO shows an excellent cycle stability. This work provides a new structure modulation route for developing high‐voltage LiCoO2 cathodes. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion batteries. The Li+ diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock‐salt phase was coherently constructed at the surface of LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−1 at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high‐rate cathode materials by tuning the surface electron transport property. [ABSTRACT FROM AUTHOR]

The cathode materials work as the host framework for both Li+ diffusion and electron transport in Li‐ion batteries. The Li+ diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock‐salt phase was coherently constructed at the surface of LiCoO2, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (Veff) imposed in the bulk, thus driving more Li+ extraction/insertion and making LiCoO2 exhibit superior rate capability (154 mAh g−1 at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high‐rate cathode materials by tuning the surface electron transport property. [ABSTRACT FROM AUTHOR]

For LiCoO 2 (LCO) operated beyond 4.55 V (vs Li/Li + ), it usually suffers from severe surface degradation. Constructing a robust cathode/electrolyte interphase (CEI) is effective to alleviate the above issues, however, the correlated mechanisms still remain vague. Herein, a progressively reinforced CEI is realized via constructing Zr─O deposits (ZrO 2 and Li 2 ZrO 3 ) on LCO surface (i.e., Z-LCO). Upon cycle, these Zr─O deposits can promote the decomposition of LiPF 6 , and progressively convert to the highly dispersed Zr─O─F species. In particular, the chemical reaction between LiF and Zr─O─F species further leads to the densification of CEI, which greatly reinforces its toughness and conductivity. Combining the robust CEI and thin surface rock-salt layer of Z-LCO, several benefits are achieved, including stabilizing the surface lattice oxygen, facilitating the interface Li + transport kinetics, and enhancing the reversibility of O3/H1-3 phase transition, etc. As a result, the Z-LCO||Li cells exhibit a high capacity retention of 84.2% after 1000 cycles in 3-4.65 V, 80.9% after 1500 cycles in 3-4.6 V, and a high rate capacity of 160 mAh g -1 at 16 C (1 C = 200 mA g -1 ). This work provides a new insight for developing advanced LCO cathodes., (© 2024 Wiley‐VCH GmbH.)

Facing the resource and environmental pressures brought by the retiring wave of lithium-ion batteries (LIBs), direct recycling methods are considered to be the next generation's solution. However, the contradiction between limited battery life and the demand for rapidly iterating technology forces the direct recovery paradigm to shift toward "direct upcycling." Herein, a closed-loop direct upcycling strategy that converts waste current collector debris into dopants is proposed, and a highly inclusive eutectic molten salt system is utilized to repair structural defects in degraded polycrystalline LiNi 0.83 Co 0.12 Mn 0.05 O 2 cathodes while achieving single-crystallization transformation and introducing Al/Cu dual-doping. Upcycled materials can effectively overcome the two key challenges at high voltages: strain accumulation and lattice oxygen evolution. It exhibits comprehensive electrochemical performance far superior to commercial materials at 4.6 V, especially its fast charging capability at 15 C, and an impressive 91.1% capacity retention after 200 cycles in a 1.2 Ah pouch cell. Importantly, this approach demonstrates broad applicability to various spent layered cathodes, particularly showcasing its value in the recycling of mixed spent cathodes. This work effectively bridges the gap between waste management and material performance enhancement, offering a sustainable path for the recycling of spent LIBs and the production of next-generation high-voltage cathodes., (© 2024 Wiley‐VCH GmbH.)

Lithium iron phosphate (LiFePO 4 , LFP) batteries are extensively used in electric vehicles and energy storage due to their good cycling stability and safety. However, the finite service life of lithium-ion batteries leads to significant amounts of retired LFP batteries, urgently required to be recycled by environmentally friendly and effective methods. Here, a direct regeneration strategy using natural and low-cost L-threonine as a multifunctional reductant is proposed. The hydroxyl groups and amino groups in L-threonine act as electron donors and nitrogen sources, respectively. The reductive environment created by L-threonine not only aids in converting the degraded FePO 4 phase back to a single LFP phase but also facilitates the elimination of detrimental Li-Fe anti-site defects; thus, reconstructing fast Li + diffusion channels. Meanwhile, N atoms derived from amino groups are able to dope into carbon layers, generating more active sites and enhancing the conductive properties of LFP particles. The regenerated LFP shows great electrochemical performance with a discharge capacity of 147.9 mAh g -1 at 1 C and a capacity retention of 86% after 500 cycles at 5 C. Further, this approach is also feasible for LFP black mass sourced from practical industrial dismantling lines, providing considerable prospects for the large-scale recycling of LFP batteries., (© 2023 Wiley-VCH GmbH.)

Lithium cobalt oxide (LCO) is widely used in Li-ion batteries due to its high volumetric energy density, which is generally charged to 4.3 V. Lifting the cut-off voltage of LCO from 4.3 V to 4.7 V will increase the specific capacity from 150 to 230 mAh g -1 with a significant improvement of 53%. However, LCO suffers serious problems of H1-3/O1 phase transformation, unstable interface between cathode and electrolyte, and irreversible oxygen redox reaction at 4.7 V. Herein, interface stabilization and band structure modification are proposed to strengthen the crystal structure of LCO for stable cycling of LCO at an ultrahigh voltage of 4.7 V. Gradient distribution of magnesium and uniform doping of nickel in Li layers inhibit the harmful phase transitions of LCO, while uniform LiMg x Ni 1- x PO 4 coating stabilizes the LCO-electrolyte interface during cycles. Moreover, the modified band structure improves the oxygen redox reaction reversibility and electrochemical performance of the modified LCO. As a result, the modified LCO has a high capacity retention of 78% after 200 cycles at 4.7 V in the half cell and 63% after 500 cycles at 4.6 V in the full cell. This work makes the capacity of LCO one step closer to its theoretical specific capacity., (© 2023 Wiley-VCH GmbH.)

The cathode materials work as the host framework for both Li + diffusion and electron transport in Li-ion batteries. The Li + diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock-salt phase was coherently constructed at the surface of LiCoO 2 , promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (V eff ) imposed in the bulk, thus driving more Li + extraction/insertion and making LiCoO 2 exhibit superior rate capability (154 mAh g -1 at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high-rate cathode materials by tuning the surface electron transport property., (© 2023 Wiley-VCH GmbH.)