Opportunities and Challenges of Li2 C4 O4 as Pre-Lithiation Additive for the Positive Electrode in NMC622||Silicon/Graphite Lithium Ion Cells

Active Organic Salts Enabling Non-Intrusive Electrolyte Presodiation Strategy

Na-ion batteries show great promise, but their practical utilization is hindered by irreversible Na-ion loss during cell formation, resulting in initial coulombic efficiencies typically below 80%. Conventional presodiation methods, which involve solid additives in the cathode, can compromise electrode integrity and leave deteriorated residues, especially with high Na ion compensation (20%). An electrolyte presodiation approach is introduced that utilizes sodium thiocyanate (NaSCN) as an electrolyte additive, discovered through cheminformatics and machine learning. This organic salt decomposes at 3.3-4.0 V, releasing active Na ions and forming a cosolvent without damaging the electrode and the cell, as confirmed by spectroscopic and microscopic analyses. The method improves the initial coulombic efficiency of a hard carbon|P2-Na2/3Ni1/3Mn1/3Ti1/3O2 pouch cell from 80.8% to 95.2%, with a capacity retention of 84.5% over 400 cycles. These findings present a practical and non-intrusive way to address Na-ion deficiency challenges in Na-ion batteries.

Sacrificial Prelithiation Using Different Lithium Salt-Coated LNMO Cathodes for Stabilizing the Electrode Structure and Enhancing Battery Performance

The cobalt-free, high-voltage spinel-type cathode LiNi0.5Mn1.5O4 (LNMO) exhibits high energy and power densities, rendering it a promising candidate for incorporation into next-generation lithium-ion batteries (LIBs). However, its high operating voltage of 4.7 V can lead to electrolyte decomposition, causing structural damage. In addition, the irreversible loss of active lithium in the early cycles reduces capacity performance, hindering its commercial application. To take full advantage of the catalytic effect of LNMO and the prelithiation of sacrificial salt, this work involved blending sacrificial salts (Li2C2O4, Li2CO3, and CH3COOLi) with LNMO to form prelithiated electrodes (LNMO-Sac) and investigating the influence of different sacrificial salts on the performance of LIBs. The results demonstrate that LNMO could efficiently catalyze the decomposition of sacrificial salts and promote the formation of a more stable electrode-electrolyte interface after cycling to mitigate structure destruction of electrodes caused by electrolyte decomposition. Compared with other sacrificial salts, Li2C2O4 provided a highly efficient supplement of active lithium and improved the electrochemical performance of the battery. Thus, LNMO-Li2C2O4 achieved an excellent discharge capacity of 137.9 mAh g-1 at 1C, and capacity retention of 85.9% after 500 cycles, superior to that of LNMO without prelithiation. Moreover, the LNMO-LO/Gr full cell presented an initial capacity of 117.9 mAh g-1 and retained 79.4 mAh g-1 after 300 cycles. This work demonstrates the feasibility of a sacrificial salt as a lithium replenishment strategy for LNMO in practical applications.

Janus-Architectured Lithium Replenishment Separators Boosting Longevity of Anode-Free Lithium Metal Batteries

Addressing the issue of inactive dead lithium deposition on the anode side remains a significant challenge for anode-free lithium metal batteries. While lithium compensation techniques can mitigate lithium depletion, directly introducing lithium compounds into the cathode material may degrade the electrode structure. Here the design and fabrication of a novel lithium replenishment separator (LRS) using a lithium compensation agent of Li2C4O4 is reported. The electrospun LRS demonstrates excellent ionic conductivity of 1.82 mS cm-1 and a high Li+ transference number of 0.51. Such a functionalized LRS not only provides additional active lithium for anode-free lithium metal batteries but also promotes uniform deposition of lithium metal. Compared with conventional polyolefin-based separators, the LRS effectively boosts LiFePO4||Cu anode-free batteries with enhanced cyclability. These results suggest this LRS strategy can find promising applications in next-generation anode-free batteries with high energy densities.

Coassembly of Ultrathin Lithium with Dual Lithium-Free Electrodes for Long-Lasting Sulfurized Polyacrylonitrile Batteries

With the rising demand for long-term grid energy storage, there is an increasing need for sustainable alternatives to conventional lithium-ion batteries. Electrode materials composed of earth-abundant elements are appealing, yet their lithiated-state stability hampers direct battery applications. In this paper, we propose for the first time a concept of coassembling ultrathin lithium with both lithium-free cathodes and lithium-free anodes to build high-energy, long-lasting, safe, and low-cost batteries tailored for long-duration energy storage. As a proof-of-concept, we selected sulfurized polyacrylonitrile (SPAN) as the lithium-free cathode and graphite/silicon-carbon (Gra/SiC) as the lithium-free anode, both of which are earth abundant. This newly conceptualized configuration not only successfully prevents overprelithiation but also exhibits superior energy density (293 Wh kg-1 and 363 Wh kg-1, respectively), excellent cycle stability (1,800 cycles), and benefit of low cost and environmental sustainability. This approach fosters new opportunities for the development of lithium-free, earth-abundant electrode batteries, spurring the development of sustainable and recyclable grid energy storage systems.

Prelithiation strategies for enhancing the performance of lithium-ion batteries

During the initial cycling of lithium-ion batteries, the generation of SEI at the electrode-electrolyte interface and the occurrence of irreversible side reactions consume the active lithium, resulting in irreversible loss of volume (ICL), which may also be accompanied by electrode volume changes and structural collapse. Addressing these challenges has become critical, and pre-lithiation with additional lithium has emerged as a key way to improve battery performance. Hence, this review comprehensively analyzes and summarizes the causes of ICL in lithium-ion batteries, and systematically discusses various prelithiation methods and mechanisms of different electrode structures, especially electrodes. Moreover, we discuss the importance of developing effective electrolyte, separator, and binder pre-lithiation technologies to improve ionic conductivity and battery life. The effectiveness of each strategy in improving initial capacity and cycling stability, while addressing compatibility issues and minimizing potential side effects, is evaluated to inform the future development and large-scale application of pre-lithiation technology.

Molecular Engineering Chemical Pre-lithiation Reagent with Low Redox Potential for Graphite Anode Enables High Coulombic Efficiency

Graphite (Gr) is a low-cost and high-stability anode for lithium-ion batteries (LIBs). However, Gr anode exhibits an obstinate drawback of low initial Coulombic efficiency (ICE), owing to the active lithium loss for the solid electrolyte interphase (SEI) layer. Herein, a straightforward and effective chemical pre-lithiation strategy is proposed to compensate for the lithium loss. A molecular engineering phenanthrene-based lithium-arene complex (Ph-based LAC) reagent is designed by density functional theory (DFT) calculations. The engineering Ph-based reagent enhances the stability of the π-electron system and the electron-donating capacity, resulting in a reduced redox potential to facilitate lithium transfer. The electrochemical distinct of the Ph-based reagent is illustrated, the prelithiation process in a low Li-insertion platform, and the lithiation degree is controllable with the dipping time (ICE = 102%, 3 min). Notably, a denser and homogeneous SEI layer has pre-formed to enhance the Li+ transport and interface stability. Moreover, the lithium-ion full batteries assemble with LiFePO4 and NCM811 cathode, which exhibits high ICE (96.5% and 90.3%) and energy density (310 and 333 Wh kg-1). These findings present a facile and controllable pre-lithiation strategy to compensate for the lithium of LIBs, providing new valuable insights into the design and optimization of battery manufacture.

How Does Li2C4O4 Prelithiation Additive Influence the Solid Electrolyte Interphase of Dual Carbon Lithium-Ion Capacitors?

Prelithiation is a critical step in dual carbon lithium-ion capacitors (LICs) due to the lack of Li+ in the system, which needs to be incorporated externally to avoid electrolyte depletion. Several prelithiation techniques have been developed over the years, and recently, dilithium squarate (Li2C4O4) has been reported as an air-stable, easy to synthesize, safe, and cost-effective prelithiation reagent for LICs. Li2C4O4 has successfully been used in a wide range of chemistries, and its integration into positive electrodes has been scaled up to roll-to-roll processing and demonstrated in multilayer pouch cells. However, its influence in the solid electrolyte interphase (SEI) has not yet been studied. In this work, the SEI formed on the hard carbon (HC) negative electrode when using Li2C4O4 as a prelithiation agent has been studied by X-ray photoelectron spectroscopy (XPS). The electrode surface has been analyzed in the lithiated and delithiated states along the first lithiation cycle, as well as at the end of the prelithiation protocol, to gain insight into the SEI formation and evolution during the prelithiation process. In addition, an aging test has been carried out to study the long-term SEI stability. We have observed that the use of Li2C4O4 induces a chemical modification in the composition of the SEI with respect to the SEI that forms by using a standard electrochemical prelithiation process, resulting in a less soluble interface. Therefore, the chemical composition of the SEI is stable over cycling. Those findings confer to Li2C4O4 the ability to tune the SEI of the devices, enabling its use in LICs and LIBs not only as a prelithiation agent but also as a film-forming additive.

An XPS Study of Electrolytes for Li-Ion Batteries in Full Cell LNMO vs Si/Graphite

Two different types of electrolytes (co-solvent and multi-salt) are tested for use in high voltage LiNi0.5Mn1.5O4||Si/graphite full cells and compared against a carbonate-based standard LiPF6 containing electrolyte (baseline). Ex situ postmortem XPS analysis on both anodes and cathodes over the life span of the cells reveals a continuously growing SEI and CEI for the baseline electrolyte. The cells cycled in the co-solvent electrolyte exhibited a relatively thick and long-term stable CEI (on LNMO), while a slowly growing SEI was determined to form on the Si/graphite. The multi-salt electrolyte offers more inorganic-rich SEI/CEI while also forming the thinnest SEI/CEI observed in this study. Cross-talk is identified in the baseline electrolyte cell, where Si is detected on the cathode, and Mn is detected on the anode. Both the multi-salt and co-solvent electrolytes are observed to substantially reduce this cross-talk, where the co-solvent is found to be the most effective. In addition, Al corrosion is detected for the multi-salt electrolyte mainly at its end-of-life stage, where Al can be found on both the anode and cathode. Although the co-solvent electrolyte offers superior interface properties in terms of the limitation of cross-talk, the multi-salt electrolyte offers the best overall performance, suggesting that interface thickness plays a superior role compared to cross-talk. Together with their electrochemical cycling performance, the results suggest that multi-salt electrolyte provides a better long-term passivation of the electrodes for high-voltage cells.

Lithium Pre-Storage Enables High Initial Coulombic Efficiency and Stable Lithium-Enriched Silicon/Graphite Anode

Application of silicon-based anodes is significantly challenged by low initial Coulombic efficiency (ICE) and poor cyclability. Traditional pre-lithiation reagents often pose safety concerns due to their unstable chemical nature. Achieving a balance between water-stability and high ICE in prelithiated silicon is a critical issue. Here, we present a lithium-enriched silicon/graphite material with an ultra-high ICE of ≥110 % through a high-stable lithium pre-storage methodology. Lithium pre-storage prepared a nano-drilled graphite material with surficial lithium functional groups, which can form chemical bonds with adjacent silicon during high-temperature sintering. This results in an unexpected O-Li-Si interaction, leading to in situ pre-lithiation of silicon nanoparticles and providing high stability in air and water. Additionally, the lithium-enriched silicon/graphite materials impart a combination of high ICE, high specific capacity (620 mAh g-1), and long cycling stability (>400 cycles). This study opens up a promising avenue for highly air- and water-stable silicon anode prelithiation methods.

Designer Lithium Reservoirs for Ultralong Life Lithium Batteries for Grid Storage

The minimization of irreversible active lithium loss stands as a pivotal concern in rechargeable lithium batteries, particularly in the context of grid-storage applications, where achieving the utmost energy density over prolonged cycling is imperative to meet stringent demands, notably in terms of life cost. Departing from conventional methodologies advocating electrode prelithiation and/or electrolyte additives, a new paradigm is proposed here: the integration of a designer lithium reservoir (DLR) featuring lithium orthosilicate (Li4SiO4) and elemental sulfur. This approach concurrently addresses active lithium consumption through solid electrolyte interphase (SEI) formation and mitigates minor yet continuous parasitic reactions at the electrode/electrolyte interface during extended cycling. The remarkable synergy between the Li-ion conductive Li4SiO4 and the SEI-favorable elemental sulfur enables customizable compensation kinetics for active lithium loss throughout continuous cycling. The introduction of a minute quantity of DLR (3 wt% Li4SiO4@S) yields outstanding cycling stability in a prototype pouch cell (graphite||LiFePO4) with an ampere-hour-level capacity (≈2.3 Ah), demonstrating remarkable capacity retention (≈95%) even after 3000 cycles. This utilization of a DLR is poised to expedite the development of enduring lithium batteries for grid-storage applications and stimulate the design of practical, implantable rechargeable batteries based on related cell chemistries.

Harmless pre-lithiation via advantageous surface reconstruction in sacrificial cathode additives for lithium-ion batteries

Sacrificial cathode additives have emerged as a tempting strategy to compensate the initial capacity loss (ICL) in Li-ion batteries (LIBs) manufacturing. However, the utilization of sacrificial cathode additives inevitably brings residuals, side reactions, and negative impacts in which relevant researches are still in the early stage. In this study, we conduct a systematic investigation on the effects of employing a nickel-based sacrificial additive, Li2Cu0.1Ni0.9O2 (LCNO), and propose a feasible strategy to achieve advantageous surface reconstruction on LCNO. Specifically, we build a Li5AlO4 (LAO) coating layer on the LCNO through dry ball milling and annealing treatment. This process not only consumes surface residual lithium compounds on LCNO but also demonstrates minimal detrimental effects on its performance. The surface reconstructed LCNO (SR-LCNO) reveals mitigated gas generation and suppressed structure degradation under high working voltage (＞4.1 V), thereby causing negligible negative effects on the cycling capability and rate performance of commercial cathode materials. The full cells containing SR-LCNO deliver significantly improved electrochemical properties, with no observed exacerbation of side reactions. This work awakes the awareness of the prudent utilization of sacrificial cathode additives and provides an effective strategy for harmless pre-lithiation via surface reconstructed sacrificial cathode additives.

Critical Review of Emerging Pre-metallization Technologies for Rechargeable Metal-Ion Batteries

Low Coulombic efficiency, low-capacity retention, and short cycle life are the primary challenges faced by various metal-ion batteries due to the loss of corresponding active metal. Practically, these issues can be significantly ameliorated by compensating for the loss of active metals using pre-metallization techniques. Herein, the state-of-the-art development in various pr-emetallization techniques is summarized. First, the origin of pre-metallization is elaborated and the Coulombic efficiency of different battery materials is compared. Second, different pre-metallization strategies, including direct physical contact, chemical strategies, electrochemical method, overmetallized approach, and the use of electrode additives are summarized. Third, the impact of pre-metallization on batteries, along with its role in improving Coulombic efficiency is discussed. Fourth, the various characterization techniques required for mechanistic studies in this field are outlined, from laboratory-level experiments to large scientific device. Finally, the current challenges and future opportunities of pre-metallization technology in improving Coulombic efficiency and cycle stability for various metal-ion batteries are discussed. In particular, the positive influence of pre-metallization reagents is emphasized in the anode-free battery systems. It is envisioned that this review will inspire the development of high-performance energy storage systems via the effective pre-metallization technologies.