LiFePO4 Cathode Research Articles

Potential regulation strategy enables ferrocene as p-type redox mediator for direct regeneration of spent LiFePO4 cathode

Conventional metallurgical technologies for recycling cathode materials from retired Li-ion batteries go against carbon neutrality owing to massive material input and energy consumption. Although featuring with simplified process, direct regeneration technology still fails to bypass high-temperature driving forces for Li+ compensation of degraded cathodes. Herein, chemical re-lithiation strategy mediated by ferrocene is proposed to directly regenerate the Li-deficient spent cathodes. Ferrocene and its derivatives, the so-called p-type redox mediators, can be oxidized spontaneously from neutral molecules to stable cations under ambient conditions, allowing them to function as electron donors. Meanwhile, lithium salts serve as Li+ donors to ensure charge neutrality of the cathode lattice. The effects of solvation and substituent are thoroughly investigated to precisely regulate the potential of a series of ferrocene-based reductants. Chemical re-lithiation is driven thermodynamically by the intrinsic potential gap between ferrocene and degraded cathodes, thus fundamentally realizing a rapid lithiation reaction (taking less than 20 min at 25 °C), while avoiding the involvement of high-temperature operation. Diverse characterizations have been performed to explore the Li+-electron concerted re-lithiation mechanism. The regenerated LiFePO4 cathode demonstrated comparable Li+ storage capability to commercial cathode. Life-cycle analysis verifies the economical and environmental superiority of our chemical re-lithiation strategy to metallurgy in practical industry. The thermodynamically spontaneous chemical re-lithiation provides competitive options for greener recycling of retired batteries in the future.

A Review of Capacity Fade Mechanism and Promotion Strategies for Lithium Iron Phosphate Batteries

Commercialized lithium iron phosphate (LiFePO4) batteries have become mainstream energy storage batteries due to their incomparable advantages in safety, stability, and low cost. However, LiFePO4 (LFP) batteries still have the problems of capacity decline, poor low-temperature performance, etc. The problems are mainly caused by the following reasons: (1) the irreversible phase transition of LiFePO4; (2) the formation of the cathode–electrolyte interface (CEI) layer; (3) the dissolution of the iron elements; (4) the oxidative decomposition of the electrolyte; (5) the repeated growth and thickening of the solid–electrolyte interface (SEI) film on the anode electrode; (6) the structural deterioration of graphite anodes; (7) the growth of lithium dendrites. In order to eliminate the problems, methods such as the modification, doping, and coating of cathode materials, electrolyte design, and anode coating have been studied to effectively improve the electrochemical performance of LFP batteries. This review briefly describes the working principle of the LFP battery, the crystal structure of the LFP cathode material, and its electrochemical performance as a cathode. The performance degradation mechanism of LFP batteries is summarized in three aspects—cathode material, anode material, and electrolyte—and the research status of LFP material modification and electrolyte design is emphatically discussed. Finally, the challenges and future development of LFP batteries are prospected.

A novel embedded KVO3/NC anode for high-performance lithium-ion batteries

Vanadium-based metallic salts, characterized by their intrinsic low electronic conductivity, are impeding their advancement as anode materials in the realm of lithium-ion battery technology. This study presents a novel embedded anode material KVO3/NC (KVO/NC) synthesized via a sol–gel method, with KVO3 (KVO) particles in situ growing on N-doped carbon, thereby ameliorating conductivity and electrochemical performance. The findings reveal that KVO/NC composite has three lithium-ion storage sites, ultra-high cycling stability (289 mA h/g@5000 cycles@10 C@100 %), and superior rate performance (249 mA h/g@15 C; 221 mA h/g@20 C). Coupled with LiFePO4 cathode, it achieves a competitive energy density (391 W h kg−1@0.1 C; 1–3.9 V). This work reveals the practical potential of KVO/NC as a new type of lithium-ion battery anode material with high energy density and long cycle life through a series of ex situ/in situ characterizations.

Dynamic Adaptive Porous Cu Current Collector for Low N/P Ratio Li Metal Batteries

AbstractPorous copper (Cu) current collectors effectively suppress the growth of lithium (Li) dendrites and enhance the stability of Li metal anodes. However, the current development of porous Cu hosts generally involves a high proportion of Cu, mostly rigid structures, small pore volumes, and low Li utilization. Here, we propose a dynamic adaptive porous Cu (DAP−Cu) host, which is lightweight with a high pore volume, fabricated using a large aspect ratio of Cu nanowires as the building blocks. This DAP−Cu allows for the precise loading of metallic Li, and the symmetric battery assembled with Li/DAP−Cu electrode operates at the high current density of 5 mA cm−2 for 4000 hours while exhibiting a low polarization voltage of ~60 mV. The Li/DAP−Cu anode achieves high‐performance compatibility with LiFePO4 and sulfur cathodes, with optimal N/P ratios of 1.20 : 1 and 4.0 : 1, respectively. Full and pouch cells with low N/P ratios exhibit exceptionally high specific capacities and long‐term cycling life. The establishment of standards for the matching of anodes and cathodes provides a reference for the quantitative preparation of electrode materials and is of significant guidance for enhancing the efficient utilization of metallic Li.

Micrometer-sized 3D porous structure decorated with uniform InSb alloy layer towards dendrite-free Li metal electrode

Li metal electrode is expected to be one promising anode to construct high energy density batteries because of its high theoretical specific capacity and the lowest electrode potential. However, uncontrollable dendrite growth and large volume changes cause batteries failure and safety risks. Here, an InSb alloy modified three-dimensional porous Cu (3D Cu@InSb) is constructed by electroless plating coupled with electroplating to stabilize the Li metal electrode. The suitable 3D porous structure with pore size of several micrometers can provide uniform current distribution, rapid ionic transferring channels, and effectively accommodate volumetric changes and release stress as well, avoiding the limited modifying effect using too large pores and poor ionic transport kinetics using too small pores. Moreover, the InSb alloy modified layer with high binding energy to Li+ reduces the nucleation overpotential and enhances the Li plating/stripping reversibility. Under the synergistic effects of InSb alloy modified layer and suitable 3D porous structure, Li metal is uniformly plated/stripped in pores with almost thorough flat surface even under a high area capacity of 4 mAh cm−2. The full battery assembled using LiFePO4 (LFP) cathode demonstrates a long life of 600 cycles at 2 C with a capacity retention of 86 %.

Modulating porous silicon-carbon anode stability: Carbon/silicon carbide semipermeable layer mitigates silicon-fluorine reaction and enhances lithium-ion transport

Silicon-based material is regarded as one of the most promising anodes for next-generation high-performance lithium-ion batteries (LIBs) due to its high theoretical capacity and low cost. Harnessing silicon carbide's robustness, we designed a novel porous silicon with a sandwich structure of carbon/silicon carbide/Ag-modified porous silicon (Ag-PSi@SiC@C). Different from the conventional SiC interface characterized by a frail connection, a robust dual covalent bond configuration, dependent on SiC and SiOC, has been successfully established. Moreover, the innovative sandwich structure effectively reduces detrimental side reactions on the surface, eases volume expansion, and bolsters the structural integrity of the silicon anode. The incorporation of silver nanoparticles contributes to an improvement in overall electron transport capacity and enhances the kinetics of the overall reaction. Consequently, the Ag-PSi@SiC@C electrode, benefiting from the aforementioned advantages, demonstrates a notably elevated lithium-ion mobility (2.4 * 10−9 cm2·s−1), surpassing that of silicon (5.1 * 10−12 cm2·s−1). The half-cell featuring Ag-PSi@SiC@C as the anode demonstrated robust rate cycling stability at 2.0 A/g, maintaining a capacity of 1321.7 mAh/g, and after 200 cycles, it retained 962.6 mAh/g. Additionally, the full-cell, featuring an Ag-PSi@SiC@C anode and a LiFePO4 (LFP) cathode, exhibits outstanding longevity. Hence, the proposed approach has the potential to unearth novel avenues for the extended exploration of high-performance silicon-carbon anodes for LIBs.

Self‐Supporting Solid Electrolyte Based on Supramolecular Interaction for Stable Li Metal Batteries

AbstractLi metal batteries based on solid polymer electrolytes offer the benefits of high energy density and safety, as well as extended cycling life, making them an excellent candidate for the next‐generation battery system. However, current solid polymer electrolytes still suffer from low ion conductivity and Li+ transfer number, which seriously restricts its practical application. Herein, a self‐supporting composite solid polymer electrolyte was prepared, where phenolic resin rich in hydroxyl groups (BR) and polyethylene oxide (PEO) are mixed evenly and poured onto a cellulose membrane in one step. In such an electrolyte, PEO and BR combine to form intermolecular hydrogen bonds, lowering the crystallinity of PEO and increasing the Li+ transfer number. Lastly, the obtained solid electrolytes exhibited a high ion conductivity (1.1×10−4 S cm−1) and Li+ transfer number (0.53), as well as improved electrochemical window. Consequently, Li || Li symmetrical cells can run stably for more than 700 h at 0.1 mA cm−2/0.25 mAh cm−2. And full cells with LiFePO4 cathode can also demonstrate high discharge capacity of 152.12 mAh g−1 and rate performance. We believe that such a design based on supramolecular interaction offer a new avenue to advanced solid polymer electrolytes.

Rapid Release of Silicon by Ultrafast Joule Heating Generates Mechanically Stable Shell-Shell Si/C Anodes with Dominant Inward Deformation.

As a promising anode material, silicon-carbon composites encounter great challenges related to internal stress release and contact between the composites during lithiation. These issues lead to material degradation and concomitantly rapid capacity decline. Here, we report a type of shell-shell silicon-carbon (SS-Si/C) composite, which consists of a carbon shell tightly coated with a silicon shell. The mechanical analysis unveils that the dominant inward expansion of the Si shell is achieved through the synergistic effect of the outer carbon shell and the inner hollow structure. Benefiting from the well-tailored shell-shell structure, the SS-Si/C anode exhibits exceptional performance, boasting a high specific capacity (1690.3 mA h g-1 after 550 cycles at 0.5 A g-1), a high areal capacity (2.05 mA h cm-2 after more than 400 cycles at 0.5 mA cm-2), and an extended cycling life (1055.6 mA h g-1 after 1000 cycles at 8 A g-1), far exceeding commercially available Si/C anodes. Using the well-designed SS-Si/C anode, full cells assembled with LiCoO2 (LCO) or LiFePO4 (LFP) cathodes achieve favorable rate capability and cyclic stability. Notably, at a high rate of 6 C (1 C = 170 and 270 mA g-1 for LFP and LCO, respectively), these full cells deliver high specific capacities of 79.5 mA h g-1 and 64.9 mA h g-1 when using LCO and LFP, respectively, demonstrating the potential of SS-Si/C anodes for practical applications. The straightforward and safe synthesis method in this work enables the rational design of hollow structures with distinct properties.

Revisiting porous foam Cu host based Li metal anode: The roles of lithiophilicity and hierarchical structure of three-dimensional framework

Lithium (Li) metal anode (LMA) is one of the most promising anodes for high energy density batteries. However, its practical application is impeded by notorious dendrite growth and huge volume expansion. Although the three-dimensional (3D) host can enhance the cycling stability of LMA, further improvements are still necessary to address the key factors limiting Li plating/stripping behavior. Herein, porous copper (Cu) foam (CF) is thermally infiltrated with molten Li-rich Li-zinc (Li-Zn) binary alloy (CFLZ) with variable Li/Zn atomic ratio. In this process, the LiZn intermetallic compound phase self-assembles into a network of mixed electron/ion conductors that are distributed within the metallic Li phase matrix and this network acts as a sublevel skeleton architecture in the pores of CF, providing a more efficient and structured framework for the material. The as-prepared CFLZ composite anodes are systematically investigated to emphasize the roles of the tunable lithiophilicity and hierarchical structure of the frameworks. Meanwhile, a thin layer of Cu-Zn alloy with strong lithiophilicity covers the CF scaffold itself. The CFLZ with high Zn content facilitates uniform Li nucleation and deposition, thereby effectively suppressing Li dendrite growth and volume fluctuation. Consequently, the hierarchical and lithiophilic framework shows low Li nucleation overpotential and highly stable Coulombic efficiency (CE) for 200 cycles in conventional carbonate based electrolyte. The full cell coupled with LiFePO4 (LFP) cathode demonstrates high cycle stability and rate performance. This work provides valuable insights into the design of advanced dendrite-free 3D LMA toward practical application.

Enhanced electrochemical performance of a LiFePO4 cathode with an environmentally friendly pectin/polyethylene glycol binder

The advancement of lithium-ion battery technology relies on the development of materials that not only improve performance but also align with environmental sustainability. This work presents a novel water-based pectin-PEG binder for LiFePO4 cathodes that combines eco-friendliness with electrochemical innovation. The binder material is made by mixing pectin, a flexible natural substance, with polyethylene glycol through a radical copolymerization process. This combination gives the binder both flexibility and a boost in electrical performance. Our experimental results demonstrate that LFP cathodes with this binder have an intriguing self-healing ability in comparison with the conventional PVDF binder, enhanced charge-discharge capacities, improved cycling stability, and higher ionic conductivity. Specifically, electrodes utilizing the pectin-PEG binder exhibit an impressive retention of discharge capacity. They maintain roughly 150 mAh g−1 after 500 cycles at 1C with 99% retention, and about 141 mAh g−1 with 97% retention at 3C. Cyclic voltammetry (CV) confirms that the PP binder maintains its ionic diffusion properties at high sweep rates, whereas galvanostatic intermittent titration technique reveals a much higher lithium ion diffusion coefficient (DLi+) within the operational voltage range of the LFP-PP250 electrodes. These findings establish an attractive direction for the development of electrodes for high-energy density, sustainable lithium-ion batteries.

Biomass-Derived Carbon Utilization for Electrochemical Energy Enhancement in Lithium-Ion Batteries.

Cathodes made of LiFePO4 (LFP) offer numerous benefits including being non-toxic, eco-friendly, and affordable. The distinctive olivine structure of LFP cathodes contributes to their electrochemical stability. Nonetheless, this structure is also the cause of their low ionic and electronic conductivity. To enhance these limitations, an uncomplicated approach has been effectively employed. A straightforward solid-state synthesis technique is used to apply a coating of biomass from potato peels to the LFP cathode, boosting its electrochemical capabilities. Potato peels contain pyridinic and pyrrolic nitrogen, which are conducive to ionic and electronic movement and facilitate pathways for lithium-ion and electron transfer, thus elevating electrochemical performance. When coated with nitrogen-doped carbon derived from potato peel biomass (PPNC@LFP), the LFP cathode demonstrates an improved discharge capacity of 150.39 mAh g-1 at a 0.1 C-rate and 112.83 mAh g-1 at a 1.0 C-rate, in contrast to the uncoated LFP which shows capacities of 141.34 mAh g-1 and 97.72 mAh g-1 at the same rates, respectively.

Fluorine-Doped Li7La3Zr2O12 Fiber-Based Composite Electrolyte for Solid-State Lithium Batteries with Enhanced Electrochemical Performance.

Garnet-based electrolytes with high ionic conductivity and excellent stability against lithium metal anodes are promising for commercial applications in solid-state lithium batteries (SSLBs). However, the further development of SSLBs is inhibited by issues such as low ionic conductivity and uncontrolled lithium dendrite growth. Herein, we report the synthesis of fluorine-doped Li7La3Zr2O12 (LLZO-F0.2) fibers by electrospinning and the subsequent calcination at high temperatures. The solid composite electrolyte with LLZO-F0.2 exhibits an ionic conductivity of 5.37 × 10-4 S cm-1 and a high lithium-ion transference number of 0.61 at room temperature. Meanwhile, it exhibits lower resistance and more uniform lithium metal stripping and deposition in symmetric cells. The full cell with LiFePO4 cathode exhibits excellent rate capability and cycling stability for 800 cycles at 0.5 C with a discharge specific capacity retention of 97.7%. This fluorine-doped fibrous garnet-type electrolyte provides a viable option for preparing high-performance SSLBs.

Improving the Ionic Conductivity and Anode Interface Compatibility of LLZO/PVDF Composite Polymer Electrolytes by Compositional Tuning.

Utilizing aluminum-doped nano LLZO (Li6.28La3Zr2Al0.24O12) as the ceramic filler, we synthesized and optimized LLZO/PVDF/LiClO4 composite polymer electrolytes (CPEs) to achieve high ionic conductivity and good interfacial stability with metallic lithium. The research examines how the PVDF grade and the mass ratio of PVDF to LiClO4 affect the ionic conductivity, lithium metal compatibility, and overall performance of CPEs. The CPE using Kynar PVDF 741 and a PVDF-to-LiClO4 mass ratio of 2:1 emerged as superior, displaying a high ionic conductivity at room temperature (0.12 mS/cm), the lowest activation energy (0.247 eV), an extensive electrochemical stability window (approximately 4.9 V), and robust mechanical strength. In tests with lithium metal symmetric cells, the membrane facilitated over 1000 h of stable cycling at 0.1 mA cm-2 and 0.1 mAh cm-2. Furthermore, when integrated into full solid-state lithium-metal batteries with LiFePO4 cathodes, it sustained more than 80% capacity retention across 500 charge/discharge cycles at a rate of 0.5 C with constantly high Coulombic efficiencies above 99.8%, underscoring its exceptional durability and efficiency. This research provides a practical framework and benchmarks for developing LLZO/PVDF-based CPEs with high ionic conductivity and enhanced stability against lithium metals.

Designing the Interface Layer of Solid Electrolytes for All-Solid-State Lithium Batteries.

Li1.3Al0.3Ti1.7(PO4)3 (LATP) is one of the most attractive solid-state electrolytes (SSEs) for application in all-solid-state lithium batteries (ASSLBs) due to its advantages of high ionic conductivity, air stability and low cost. However, the poor interfacial contact and slow Li-ion migration have greatly limited its practical application. Herein, a composite ion-conducting layer is designed at the Li/LATP interface, which a MoS2 film is constructed on LATP via chemical vapor deposition, followed by the introduction of a solid polymer (SP) liquid precursor to form a MoS2@SP protective layer. This protective layer not only achieves a lower Li-ion migration energy barrier, but also adsorbs more Li-ion, which is able to promote interfacial ion transport and improve interfacial contacts. Thanks to the improved migration and adsorption of Li-ion, the Li symmetric cell containing LATP-MoS2@SP exhibits a stable cycle of more than 1200h at 0.1mAcm-2. More remarkably, the capacity retention of the full cell assembled with LiFePO4 cathode is as high as 86.2% after 400 cycles at 1C. This work provides a design strategy for significantly improving unstable interfaces of SSEs and realizing high-performance ASSLBs.

Laser‐Constructing 3D Copper Current Collector with Crystalline Orientation Selectivity for Stable Lithium Metal Batteries

The practical application of lithium (Li) metal anodes in high‐capacity batteries is impeded by the formation of hazardous Li dendrites. To address this challenge, this research presents a novel methodology that combines laser ablation and heat treatment to precisely induce controlled grain growth within laser‐structured grooves on copper (Cu) current collectors. Specifically, this approach enhances the prevalence of Cu (100) facets within the grooves, effectively lowering the overpotential for Li nucleation and promoting preferential Li deposition. Unlike approaches that modify the entire surface of collectors, our work focuses on selectively enhancing lithiophilicity within the grooves to mitigate the formation of Li dendrites and exhibit exceptional performance metrics. The half‐cell with these collectors maintains a remarkable Coulombic efficiency of 97.42% over 350 cycles at 1 mA cm−2. The symmetric cell can cycle stably for 1600 h at 0.5 mA cm−2. Furthermore, when integrated with LiFePO4 cathodes, the full‐cell configuration demonstrates outstanding capacity retention of 92.39% after 400 cycles at a 1C discharge rate. This study introduces a novel technique for fabricating selective lithiophilic three‐dimensional (3D) Cu current collectors, thereby enhancing the performance of Li metal batteries. The insights gained from this approach hold promise for enhancing the performance of all laser‐processed 3D Cu current collectors by enabling precise lithiophilic modifications within complex structures.

On-surface conversion reaction realizes advanced red phosphorus/carbon anode for high-performance lithium-ion batteries

Red phosphorus (RP), the one of the most prospective anodes in lithium-ion batteries (LIBs), has been severely limited due to the intrinsic defects of massive volume expansion and low electronic conductivity. The vaporization-condensation-conversion (VCC), which confines RP nanoparticles into carbon host, is the most widely used method to address the above drawbacks and prepare RP/C nanostructured composites. However, the volume effect-dominated RP caused by the inevitably deposition of RP vapor on the surface of carbon material suffers from the massive volume change and unstable solid electrolyte interface (SEI) film. Herein, we propose a simple interfacial modification method to eliminate the superficial RP and yield stable surface composed of ion-conducting Li3PS4 solid electrolyte, endowing RP/AC composites excellent cycling performance and ultrafast reaction kinetics. Therefore, the RP/AC@S composites exhibit 926 mAh/g after 320 cycles at 0.2 A/g (running over 181 days), with 81.6 % capacity retention and a corresponding capacity decay rate of as low as 0.059 %. When coupled with LiFePO4 cathode, the full cells present superior cycling performance (62.1 mAh/g after 500 cycles at 1 A/g) and excellent rate capability (81.1 mAh/g at 1.0 A/g).

Green and high-yield recovery of phosphorus from municipal wastewater for LiFePO4 batteries

The rapidly growing demand for lithium iron phosphate (LiFePO4) as the cathode material of lithium–ion batteries (LIBs) has aggravated the scarcity of phosphorus (P) reserves on Earth. This study introduces an environmentally friendly and economical method of P recovery from municipal wastewater, providing the P source for LiFePO4 cathodes. The novel approach utilizes the sludge of Fe-coagulant-based chemical P removal (CPR) in wastewater treatment. After a sintering treatment with acid washing, the CPR sludge, enriched with P and Fe, transforms into purified P–Fe oxides (Fe2.1P1.0O5.6). These oxides can substitute up to 35% of the FePO4 reagent as precursor, producing a carbon-coated LiFePO4 (LiFePO4/C) cathode with a specific discharge capacity of 114.9 mA·h·g−1 at 0.1 C (C represents current density, 1 C equaling 170 mA·g−1) (C), and cycle stability of 99.2% after 100 cycles. The enhanced cycle performance of the as-prepared LiFePO4/C cathode may be attributed to the incorporations of impurities (such as Ca2+ and Na+) from sludge, with improved stability of crystal structure. Unlike conventional P-fertilizers, this P recovery technology converts 100% of P in CPR sludge into the production of value-added LiFePO4/C cathodes. The recovered P from municipal wastewater can meet up to 35% of the P demand in the Chinese LIBs industry, offering a cost-effective solution for addressing the pressing challenges of P scarcity.

New Lithium Solid-State Batteries with Asymmetrical Polymer Nanocomposite Electrolyte and LiFePO4 Cathode, “Liquid Phase Therapy” Effect

New Lithium Solid-State Batteries with Asymmetrical Polymer Nanocomposite Electrolyte and LiFePO4 Cathode, “Liquid Phase Therapy” Effect

Construction of multiwall carbon nanotubes/biomass-derived nitrogen-doped carbon@regenerated LiFePO4 cathode materials for lithium-ion batteries

Construction of multiwall carbon nanotubes/biomass-derived nitrogen-doped carbon@regenerated LiFePO4 cathode materials for lithium-ion batteries

Potential-Regulated Design for Direct Recycling of Degraded LiFePO4 Cathode.

The rapid proliferation of power sources equipped with lithium-ion batteries poses significant challenges in terms of post-scrap recycling and environmental impacts, necessitating urgent attention to the development of sustainable solutions. The cathode direct regeneration technologies present an optimal solution for the disposal of degraded cathodes, aiming to non-destructively re-lithiate and straightforwardly reuse degraded cathode materials with reasonable profits and excellent efficiency. Herein, a potential-regulated strategy is proposed for the direct recycling of degraded LiFePO4 cathodes, utilizing low-cost Na2SO3 as a reductant with lower redox potential in the alkaline systems. The aqueous re-lithiation approach, as a viable alternative, not only enables the re-lithiation of degraded cathode while ignoring variation in Li loss among different feedstocks but also utilizes the rapid sintering process to restore the cathode microstructure with desirable stoichiometry and crystallinity. The regenerated LiFePO4 exhibits enhanced electrochemical performance with a capacity of 144mA h g-1 at 1 C and a high retention of 98% after 500 cycles at 5 C. Furthermore, this present work offers considerable prospects for the industrial implementation of directly recycled materials from lithium-ion batteries, resulting in improved economic benefits compared to conventional leaching methods.