Element-Engineered Lithium Borate for High-Efficiency Prelithiation in Silicon-Based Lithium-Ion Batteries.

Li-rich layered oxide (LRO) cathode material is utilized in anode-free Li metal batteries to provide extra Li inventory, compensating for the constant Li loss during cycling. The Li compensation mechanism of LRO in the anode-free system is elucidated by exploring the reversible/irreversible Li consumption behaviors. Moreover, the relationship between cathode areal capacity, Li inventory, and the cycling performance of the Cu||LRO cell is quantitatively analyzed. The well-designed Cu||LRO anode-free cell demonstrates 51% capacity retention after 60 cycles at a practical areal capacity of 5.0 mAh cm-2, overwhelming the 0.6% capacity retention for Cu||NCM523. Further optimization with an artificial anode protection layer and a fully fluorinated electrolyte enhances the capacity retention of Cu||LRO to 61.4% and 71.5% after 60 cycles, respectively. Combining its low initial Coulombic efficiency and high specific energy, the LRO cathode shows great prospects in the future development of high energy and long lifespan anode-free Li metal batteries.

Double-shell Li-rich layered oxide hollow microspheres with sandwich-like carbon@spinel@layered@spinel@carbon shells as high-rate lithium ion battery cathode

Self‐supporting Sn foil is a promising high‐volumetric‐capacity anode for lithium ion batteries (LIBs), but it suffers from low initial Coulombic efficiency (ICE). Here, mechanical prelithiation is adopted to improve ICE, and it is found that Sn foils with coarser grains are prone to cause electrode damage. To mitigate damage and prepare thinner lithiated electrodes, 3Ag0.5Cu96.5Sn foil is used that has more refined grains (5–10 µm) instead of Sn (50–100 µm), where the abundant grain boundaries (GBs) offer more sliding systems to release stress and reduce deep fractures. Thus, the thickness of Lix3Ag0.5Cu96.5Sn can be reduced to 50 µm, compared to 100 µm LixSn. When the foils contact open air, the Sn‐Li‐O(H) products are more stable than Li‐O(H), thus Lix3Ag0.5Cu96.5Sn shows outstanding air stability. The as‐prepared 50 µm foil anode achieves stable 200 cycles in LiFePO4//Lix3Ag0.5Cu96.5Sn full cell (≈2.65 mAh cm−2) and the capacity retention is 95%. Even at 5C, the capacity of Lix3Ag0.5Cu96.5Sn is still up to ≈1.8 mAh cm−2. The cycle life of NCM523//Lix3Ag0.5Cu96.5Sn full cell exceeds that of NCM523//Li. Furthermore, 70 µm Lix3Ag0.5Cu96.5Sn is used as double‐sided anode for a 3 cm × 2.8 cm pouch cell and its actual volumetric capacity density is 674 mAh cm−3 after 50 cycles.

The carbon-coated silicon monoxide (SiOx@C) has been considered as one of the most promising high-capacity anodes for the next-generation high-energy-density lithium-ion batteries (LIBs). However, the relatively low initial Coulombic efficiency (ICE) and the still existing huge volume expansion during repeated lithiation/delithiation cycling remain the greatest challenges to its practical application. Here, we developed a lithium and boron (Li/B) co-doping strategy to efficiently enhance the ICE and alleviate the volume expansion or pulverization of SiOx@C anodes. The in situ generated Li silicates (LixSiOy) by Li doping will reduce the active Li loss during the initial cycling and enhance the ICE of SiOx@C anodes. Meanwhile, B doping works to promote the Li+ diffusion and strengthen the internal bonding networks within SiOx@C, enhancing its resistance to cracking and pulverization during cycling. As a result, the enhanced ICE (83.28%), suppressed volume expansion, and greatly improved cycling (85.4% capacity retention after 200 cycles) and rate performance could be achieved for the Li/B co-doped SiOx@C (Li/B-SiOx@C) anodes. Especially, the Li/B-SiOx@C and graphite composite anodes with a capacity of 531.5 mA h g-1 were demonstrated to show an ICE of 90.1% and superior cycling stability (90.1% capacity retention after 250 cycles), which is significant for the practical application of high-energy-density LIBs.

Low initial Coulombic efficiency (ICE) is an obstacle for practical application of Li-rich Mn-based layered oxides (LLOs), which is closely related with the irreversible oxygen evolution owing to the overoxidized reaction of surface labile oxygen. Here we report a NH4 F-assisted surface multicomponent integration technology to accurately control the ICE, by which oxygen vacancies, spinel-layered coherent structure, and F-doping are skillfully integrated on the surface of treated LLOs microspheres. Though the regulation on the removed amount of labile oxygen by surface integrated structure, the ICE of LLOs cathodes can adjust from starting value to 100 %. X-ray absorption spectroscopy, refined X-ray diffraction, and scanning transmission electron microscopy show that the removed labile oxygen mainly comes from Li2 MnO3 -like structure. Even operating at a high cut-off voltage of 5 V, the capacity retention of integrated sample at 200 mA g-1 is still larger than 98 % after 100 cycles.

The demand for high-performance energy storage systems has intensified the search for alternative battery technologies beyond lithium-ion batteries (LIBs). Interestingly, sodium-ion batteries (SIBs) have emerged as promising candidates due to the natural abundance and cost-effectiveness of sodium (Na) resources. However, achieving competitive energy density remains a significant challenge, particularly at the anode counterpart. Traditional carbonaceous anodes, specifically graphite, which have demonstrated remarkable success in LIBs, tend to exhibit suboptimal electrochemical performance when applied to SIBs. This limitation primarily arises from the fundamental thermodynamic and kinetic differences between lithium (Li) and Na ions. In particular, Na possesses a significantly larger ionic radius than Li, which hinders its ability to intercalate efficiently into the graphite layers typically used in LIBs. Moreover, the weaker binding affinity of Na to the carbonaceous host leads to less favorable thermodynamics, further contributing to its sluggish intercalation kinetics. These issues result in poor Na-ion storage capacity, low initial Coulombic efficiency (ICE), and rapid capacity fading. To overcome these limitations, alloy-type anode materials are gaining attention for their high theoretical capacities and enhanced energy densities. Thus, this review intends to provide a comprehensive overview of recent advances in alloy-type anodes for SIBs, focusing on elucidating and unraveling the underlying mechanisms of Na storage. Key insights into the electrochemical behavior, phase transformations, and failure mechanisms of these materials are discussed, highlighting the critical factors that influence their performance. Additionally, the review examines the fundamental science behind the performance degradation of carbonaceous anodes, providing a comparative analysis to better understand the challenges and opportunities for next-generation SIB anodes. Overall, this work aims to bridge the knowledge gap in the design of high-energy-density anodes for SIBs, guiding future developments in the quest for efficient and sustainable energy storage solutions.

Strategies for designing high-performance hard carbon anodes with enhanced lithium-ion diffusion and rate capability

Heterostructured lithium-rich layered oxides core@ spinel- MgAl2O4 shell as high-performance cathode for lithium-ion batteries

Spontaneous local redox reaction to passivate CNTs as lightweight current collector for high energy density lithium ion batteries

Interfacial oxygen coordination environment regulation towards high-performance Li-rich layered oxide cathode

Prelithiation can replenish active Li into the battery to compensate the Li consumption due to the formation of solid electrolyte interphase (SEI) on the electrode surface, therefore improving the energy density of Li-ion batteries (LIBs), especially for batteries using electrode materials with low initial Coulombic efficiency (ICE). However, practical prelithiation in LIBs is a challenge since most lithiated compounds with high specific capacity are unstable and industrially incompatible. Herein, an effective prelithiation strategy is demonstrated by using a lithium-carbon (Li-C) microsphere composite. These Li-C microspheres are passivated by a self-assembled monolayer of octadecylphosphonic acid, which suppresses the reaction between Li and commonly used slurry solvent 1-methyl-2-pyrrolidinone (NMP). After the addition of passivated Li-C into the NMP-based graphite slurry, the ICE of the graphite||Li half-cell boosts from 88.5% to 100.5%. In a 4.5V LiCoO2 (LCO)||graphite full-cell, the supplementary Li source avoids excessive delithiation of LCO, thus suppressing the destructive phase transformation at high delithiation potential. As a result, the prelithiated LCO||graphite full-cell presents an initial discharge capacity of 201mAhg-1 and the capacity retention after 100 cycles increases by 7.1%. This work provides a practical approach for developing high energy density and long cycle life LIBs.

The limited theoretical capacity of traditional cathode materials solely based on transition metal (TM) redox has been a primary factor for the ceiling placed on the energy density of LIBs. In this regard, Li-rich layered oxides (LLOs) have received a great deal of attention, due to their high reversible capacity (> 250 mAh g-1) and high energy density (900 Wh kg-1), courtesy of the TM redox and the additional high-voltage O2- redox.1, 2 Although the electrochemical performance of Co-free LLOs is significantly less satisfactory, developing Co-free cathodes is inevitably a holy grail owing to cobalt’s economic, ethical, and political issues caused by high-cost toxicity. Therefore, studies on Co-free LLOs are necessary for creating long-term benefits for the cathode industry.Unfortunately, Co-free LLOs suffer from capacity and voltage decay on cycling, which for now obviously limits the materials use outside the academics laboratory. It is well accepted that that performance decay is primarily attributed to the irreversible anionic redox and structural degradation in LLOs. The doping strategy has been widely used to address the voltage decay of LLOs.3 While the dopant is typically introduced to the layered R m component, the lithium-rich component (C2/c) in the LLOs, which is the source of anionic redox, has always been ignored.Our team comprehensively investigates the structural involution of LLOs based on a Co-free Li-rich Mn-based Li1.2Ni0.2Mn0.6O2 (LNMO) cathode using in-operando and ex-situ synchrotron-based characterizations. We learned through mechanistic characterization that the transition from the monoclinic (C2/c) to the hexagonal (R-3m) behaviour is an intrinsic behaviour of LLOs for the first time. According to this structure-function relationship, we introduced a small quantity of one electrochemically active metal, ruthenium, into both R-3m and C2/c components in LNMO and found that the oxygen lattice and structural stability can be significantly improved by the site-specific doping against lithiation and delithiation processes.4 Additionally, reducing the irreversible TM migration is key to advancing the performance of layered oxide cathode materials. Contrary to many previous studies that emphasize suppressing cation migration, our team proposed that reversible tetrahedral-octahedral TM migration helps inhibit the formation of undesirable structural changes and phase transformation. The oxidation state of TM, such as Ni, Mn, and Co, are easily trapped into the octahedral sites in the Li layer due to their high octahedral-site splitting energy when a large amount of Li has extracted from the structure. By introducing Cr into LNMO, we found that Cr can migrate reversibly between the tetrahedral and octahedral sites, which makes Cr-doped LNMO possess significantly enhanced structural stability and thus achieve higher electrochemical performance than LNMO.In all, our research focuses on the site-specific doping of the Co-free LLOs and understanding the structure- and chemistry-function relationship of the LLOs. The findings in our work might provide possible pathways for the future design of high-performance cathode materials for lithium-ion batteries and may also apply to developing cathode materials for other energy storage systems.Reference S. Hu, A. S. Pillai, G. Liang, W. K. Pang, H. Wang, Q. Li and Z. Guo, Electrochem. Energy Rev., 2019, 2, 277-311.M. Han, J. Jiao, Z. Liu, X. Shen, Q. Zhang, H.-J. Lin, C.-T. Chen, Q. Kong, W. K. Pang, Z. Guo, R. Yu, L. Gu, Z. Hu, Z. Wang and L. Chen, Adv. Energy Mater., 2020, 10, 1903634.Y. Fan, W. Zhang, Y. Zhao, Z. Guo and Q. Cai, Energy Stor. Mater., 2021, 40, 51-71.Y. Fan, E. Olsson, G. Liang, Z. Wang, A. M. D'Angelo, B. Johannessen, L. Thomsen, B. Cowie, J. Li, F. Zhang, Y. Zhao, W. K. Pang, Q. Cai and Z. Guo, Angew. Chem. Int. Ed., 2022, DOI: 10.1002/anie.202213806.

Rationally engineered amorphous TiOx/Si/TiOx nanomembrane as an anode material for high energy lithium ion battery

Biomass hard carbon of high initial coulombic efficiency for sodium-ion batteries: Preparation and application

Li‐rich cathode materials (LRMs) are regarded as the key cathode candidates for next‐generation lithium‐ion batteries(LIBs) because of their high specific capacity and environmental friendliness. However, LRMs encounter poor cyclability and low initial coulombic efficiency (ICE) hindering their practical application. Herein, a general near‐surface in situ reconstruction strategy is proposed of constructing the Li/O dual vacancies and spinel‐carbon dual coating layers on the surface of LRMs concurrently to improve Li+ storage performance. The as‐prepared LRMs exhibit a greatly strengthened specific capacity of 283 mAh g−1 with an enhanced ICE of 94% and long‐term cyclability of 91% retention after 200 cycles compared with the pristine LRMs (212 mAh g−1 with an ICE of 65%, 76% retention after 200 cycles). Furthermore, it is theoretically revealed that O vacancies (Ov) prefer to occur at the interface of the C2/m and Rm phases to mitigate lattice stress, rather the O sites in individual C2/m or Rm phase with more coordinated atoms. Besides, Li ions exhibit lower migration energy from C2/m phase to Rm phase with the Ov located at the lattice interface. Therefore, this strategy opens a new avenue in the design perspective of the LRMs’ near‐surface for high‐energy‐density LIBs.