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Preparation and Electrochemical Properties of Carbon-Coated LiMn0.6Fe0.4PO4 Cathode Material for Lithium-Ion Batteries

Yonglian Xiong,Ying Wei,Wenyi Rong,Jin Shang,Kepiao He,Ting Yi,Yongsheng Fan

The LiMnxFe1−xPO4/C (x = 0.5, 0.6, and 0.7) cathode materials for lithium-ion batteries were synthesized by polyethylene glycol (PEG) 400 as the carbon source via a combination of wet ball-milling and high-temperature solid-state reaction. The analysis results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) indicate that the as-prepared LiMn0.6Fe0.4PO4/C sample has a single-phase orthorhombic olivine structure, and the majority of particle sizes range from 100 to 200 nm with a ∼2–3 nm carbon coating layer. The electrochemical measurements demonstrate that the obtained LiMn0.6Fe0.4PO4/C composite possesses preferable Li-ion storage properties, and the discharge capacity of 137.7 mAh g−1 at 1 C rate, which is 83.6% of that at 0.1 C rate. The composite also exhibits outstanding cycling stability, with a capacity retention of 98.2% after 100 cycles at 0.2 C rate. And the differential capacity analysis (dQ/dV) reveals that the dominating degradation of LiMn0.6Fe0.4PO4/C is caused by the Mn2+ /Mn3+ redox capacity loss which is located at ∼4.12/3.96 V, whether during the charge or discharge process. Moreover, the LiMn0.6Fe0.4PO4/C sample delivers excellent high-temperature performance (45 °C), with improved reversible capacity and capacity retention of 148.7 mAh g−1 and 99.3% after 80 cycles at 0.5 C rate, respectively.

Facile synthesis and excellent electrochemical performance of LiMn0.6Fe0.4PO4/C with 3D conductive network

Tian Weichao,Zheng Yi,Zhang Kaicheng,Ren Xin,Tian Shiyu,Cao Jingrui,Wen Lizhi,Liang Guangchuan

In this paper, the LiMn 0.6 Fe 0.4 PO 4 /C with 3D conductive network was synthesized using β-cyclodextrin (β-CD) and carbon nanotubes (CNTs) as complex carbon source by a simple preparation route which include combination of wet ball milling, spray drying, and carbothermal reduction. The unique conductive network result in the composite has sufficient contact with electrolyte and three-dimensional electron conduction path. SEM and TEM images indicate that the active materials were uniformly coated by amorphous carbon and CNTs. The addition of β-CD and CNTs not only restricted growth of active particle but also reduced electron conduction distance. The composite possesses superior electron conductivity (8.8 × 10 −2 S cm −1 ) and Li + diffusion efficiency (6.1 × 10 −13 cm 2 s −1 ) due to unique 3D conductive network. As a result, the prepared sample exhibits distinguished discharge capacity of 160.2 mAh g −1 at 0.2 C and 131.7 mAh g −1 capacity even in 10 C.

Modification of LiMn0.6Fe0.4PO4 by SWNTs and amorphous carbon for high-performance lithium-ion batteries

Hai-Wen Tang,Jin-Jin Jiang,Liu-Si Yu,Hong-Lin Yu,Yun-Qian Zhong,Li-Mei Yu,Su-Jun Wang,Huan Zhang

This study presents a dual-carbon modified LiMn0.6Fe0.4PO4 cathode (LMFP/SWNT/C) through the combined integration of amorphous carbon and single-walled carbon nanotubes (SWNTs). The composite was synthesized via a solvothermal approach followed by carbonization, forming a homogeneous conductive network with enhanced graphitization (IG/ID ratio = 3.24–4.24 versus 0.98–0.99 for LMFP/C). Electrochemical characterization revealed superior performance, including a high discharge capacity of 160.8 mAh g−1 at 0.1C and excellent cycling stability (124.9 mAh g−1 with 92.6% capacity retention after 280 cycles at 1C). In-situ electrochemical impedance spectroscopy (EIS) coupled with distribution of relaxation times (DRT) analysis indicated that the addition of SWNTs could improve the electronic conductivity. These results demonstrate the effectiveness of hybrid carbon architectures for optimizing LMFP cathode materials.

Synergistic Mg and Zn dual-doping with carbon coating for advanced LiMn0.6Fe0.4PO4 cathode materials

Xie Tao,Jian Yuxuan,Wang Chuang,Pan Qingrui,Yang Lingzhuo,Long Jinxiang,Yang Fenglin,Wu Xianwen,Wu Xianming

LiMn x Fe 1 − x PO 4 (LMFP) is a promising cathode candidate due to its high working voltage, cost-effective advantages, and environmentally friendly characteristics. However, LMFP is constrained by issues such as low intrinsic electronic and ionic conductivity, as well as Jahn–Teller lattice distortion induced by Mn 3+ , which limit its practical performance. To synergistically optimize its electrochemical behavior, LiMn 0.6 − x − y Fe 0.4 Mg x Zn y PO 4 (x = 0, y = 0; x = 0.005, y = 0.005; x = 0.01, y = 0; x = 0, y = 0.01) composite materials were designed and synthesized via a solvothermal method in this study. A comparative investigation of these samples was conducted to systematically elucidate the mechanisms underlying individual Mg and Zn doping and their synergistic co-doping. The experimental results indicate that the synergistic strategy of Mg and Zn dual-doping combined with carbon coating helps stabilize the olivine structure of LMFP, improves the reaction kinetics, and lowers the Li + diffusion energy barrier. The optimized LMFP/C-MgZn1 exhibits enhanced electrochemical performance, retaining 92.42% of its capacity after 600 cycles at 1.0 C and delivering a discharge specific capacity of 109.8 mAh g −1 at 10.0 C. Furthermore, Density Functional Theory (DFT) calculations indicate that the co-doping strategy improves the reaction kinetics by reducing both the material’s band gap and the Li + diffusion energy barrier. Graphical abstract Mg Zn co doping stabilizes LMFP/C, reduces the Li diffusion barrier and band gap,and enables fast kinetics with durable cycling. The alternative text for this image may have been generated using AI.

Synergistic Ti-Ni co-doping enhances the electrochemical performance and densification of LiMn0.6Fe0.4PO4/C cathodes

Long Ye,Juntao Si,Cheng Zhang,Sihan Zeng,Chunhua Chen

Ti-Ni co-doping improves electrochemical kinetics and powder densification. • Dopants Ti and Ni function on the Mn- and Fe-redox regions, respectively. • Powder compaction density increases by 8.5% to 2.04 g cm −3 after Ti-Ni doping. LiMn 0.6 Fe 0.4 PO 4 (LMFP) is a promising high-energy cathode, but its practical application is constrained by sluggish Mn 2+ /Mn 3+ redox kinetics and insufficient powder compaction density (PCD). Herein, Ti-doped, Ni-doped, and Ti–Ni co-doped LMFP/C were prepared by a ball-milling-assisted solid-state route. It is clarified that Ni predominantly accelerates the Fe 2+ /Fe 3+ reaction, whereas Ti promotes the kinetically slower Mn 2+ /Mn 3+ reaction and improves cycling stability. The optimal sample LMFP-2Ti-2Ni delivers 163.1 and 142.9 mAh g −1 at 0.1 and 5 C, respectively, and retains 90.8% of its capacity after 400 cycles at 1 C. Relative to pristine LMFP, the Ti-Ni co-doping increases the 0.1 C capacity from 144.7 to 163.1 mAh g −1 (+12.7%) and the PCD from 1.88 to 2.04 g cm −3 (+8.5%). Also, the relative unit-cell-volume variation decreases from approximately 5.2% to 4.6%, indicating more gradual bulk-lattice evolution. Thus, Ti–Ni co-doping as a complementary strategy can simultaneously improve rate capability, cycling durability, and particle packing in LMFP/C cathodes. Download: Download high-res image (356KB) Download: Download full-size image

Synergistic Bulk and Interface Modulation of LiMn0.6Fe0.4PO4 Cathodes through Mg2+ Gradient Insertion for Enhanced Li+ Diffusion

Jiahui Xu,Meihua Chen,Xueyin Wang,Yueying Liu,Zhian Wang,Zhenguo Wu,Benhe Zhong,Tingru Chen,Xiaodong Guo

Olivine-type LiMnxFe1–xPO4 (LMFP) is a promising high-voltage cathode for next-generation lithium-ion batteries; however, its commercialization is hindered by structural instability from Mn3+ Jahn–Teller distortion and sluggish ionic kinetics. Herein, we develop a novel gradient-insertion strategy to address these limitations simultaneously. Through a facile solid-state process, Mg2+ is incorporated into LMFP microspheres, creating a concentration profile. Structural characterization confirms the successful incorporation of Mg2+, predominantly occupying the transition-metal sites, without altering the primary structure or forming a coating layer. This targeted modification significantly improves electrochemical performance: the Mg-insertion cathode (LMFP-Mg) delivers a high capacity of 149.78 mAh g–1 at 0.1 C, with the Mn redox contribution increasing significantly from 40.3% to 53.2%. After 300 cycles at 1 C, LMFP-Mg retains 91.2% of its capacity, significantly outperforming pristine LMFP (80.5%). At a high rate of 5 C, LMFP-Mg demonstrates a 26.4% improvement in discharge capacity compared to LMFP. Mechanistic studies reveal that gradient Mg2+ insertion cooperatively stabilizes the bulk lattice, suppresses Mn3+ Jahn–Teller distortion, and enhances Li+ diffusion coefficient, while the Mg-rich surface mitigates transition-metal dissolution and interfacial side reactions. This work demonstrates that spatially controlled insertion is a promising strategy for designing high-energy-density, long-life olivine cathodes.

Multifunctional Crosslinked PAA–TA Binder: Robust Structural Integrity and Suppressed Manganese Dissolution for High–Performance LiMn0.6Fe0.4PO4 Cathodes

A poly (acrylic acid–tannic acid) (PAA–TA) crosslinked composite is reported on for the first time as an aqueous binder for LiMn0.6Fe0.4PO4(LMFP) cathodes to suppress manganese dissolution. Benefiting from hydrogen bonding and chemical crosslinking, the PAA-TA binder constructs a robust three-dimensional network that strengthens the interfacial adhesion among active particles, conductive additives, and the current collector, stabilizing the LMFP crystal structure upon cycling. More importantly, this polymeric network effectively restrains manganese leaching, which is the major origin of the capacity fading of LMFP cathodes. Meanwhile, continuous electron and ion transport pathways are well established. The LMFP electrode with an optimized PA5TA1 binder delivers a reversible capacity of 112 mAh g−1at 5 C and retains 81.3% of its capacity after 300 cycles, outperforming the PVDF/LMFP electrode. Post–mortem analyses of cycled LMFP cathodes further confirm that there was substantially suppressed Mn2+dissolution in the PAA–TA electrode, corroborating the structural integrity of the cathode–electrolyte interface. This crosslinked aqueous polymer provides a sustainable alternative to the PVDF binder for long–life LMFP cathodes.

A 3D continuous mesoporous carbon framework enhances electronic/ionic kinetics of LiMn0.6Fe0.4PO4 cathode for high-performance lithium-ion batteries

Xinglin Tang,Jiaqi Huang,Fangzhou Zhao,Yuqi Zhou,Yulin Xu,Ye Tao,Wanglai Cen,Yangjie Dai,Yongzhi Zhang

LiMn 1- x Fe x PO 4 (0 < x  < 1), an olivine-type cathode material, is attracting attention due to its higher voltage and energy density. However, it is plagued by relatively low electronic and ionic kinetics. In this research, we successfully fabricated a three-dimensional (3D) continuous mesoporous carbon framework embedded with ultrafine LiMn 0.6 Fe 0.4 PO 4 /C nanoparticles (LMFP/C@MC) by introducing glucose, PEG2000, and oleic acid as composite carbon sources during the synthesis process. The ultrafine LiMn 0.6 Fe 0.4 PO 4 nanoparticles shorten electron/ion transport pathways in the bulk phase and alleviate the voltage decay caused by the structural strain resulting from the Li + insertion/extraction process. The 3D continuous carbon framework provides rapid pathways for electron transport among the particles, thereby enhancing electronic kinetics, while also adapting volume changes and preventing the agglomeration of LiMn 0.6 Fe 0.4 PO 4 nanoparticles during the charge-discharge cycling. Mesopores facilitate electrolyte penetration and Li + diffusion, thereby enhancing ionic kinetics. Due to such advantages, LMFP/C@MC exhibits an ultrahigh specific capacity of 164.69 mA h g −1 at 0.1C, an excellent rate capability of 139.79 mA h g −1 at 20 C, and cycling stability with an ultrahigh retention of capacity of 96.2 % after 500 cycles at 2 C at 25 °C. Even at 60 °C, LMFP/C@MC maintains a capacity retention rate of 96 %, significantly higher than that of commercial LiMn 0.6 Fe 0.4 PO 4 /C (C-LMFP/C, 77 %) after 500 cycles at 2 C. This study presents a possible approach to developing high-performance lithium-ion battery cathodes.

Enhancing the High-Rate Capability and Cycling Stability of LiMn0.6Fe0.4PO4/C Cathode Materials for Lithium-Ion Batteries by Na+ Doping

Jiahao Xu,Kangwei Hou,Xiaolin Li,Yuhan Bian,Yaping Wang,Li Wang,Guangchuan Liang

The practical applications of lithium manganese iron phosphate (LMFP) are severely circumvented by the inferior electronic conductivity and electrochemical reaction kinetics. In this work, a Na+-doping method is adopted to prepare Li1–xNaxMn0.6Fe0.4PO4/C (x = 0, 0.01, 0.02, 0.03) materials by spray drying combined with the carbothermal reduction method. It is found that appropriate Na+ doping enhances the crystallinity, reduces Li–Fe antisite defects, decreases the primary particle size, and homogenizes the size distribution of the LMFP material. Moreover, the inferior rate and cycling performance of LMFP are mainly ascribed to the slower Li+ diffusion kinetics of Mn redox. A combination of experiments and DFT calculations shows that Na+ doping can increase the Li–O bond length, widen the Li+ diffusion channel, and decrease Li+ diffusion energy barriers, which can accelerate the Li+ diffusion rate and Mn redox kinetics, thereby improving the high-rate capability and cycling stability of Na+-doped samples. Besides, doped Na+ can not only act as pillars to stabilize the structure but also reduce Mn3+ content and Mn–Mn interactions to alleviate the Jahn–Teller effect, which also helps to improve the cycling performance of Na+-doped samples, wherein the Li0.98Na0.02Mn0.6Fe0.4PO4/C sample exhibits optimal rate and cycling performances. Its specific discharge capacity is 125.0 mAh g–1 at 5 C, and the capacity retention rate reaches 96.7% after 100 cycles at 1 C. Therefore, the Na+-doping strategy is believed to be an effective modification means to ameliorate the high-rate and cycling capabilities of olivine-based cathode materials.

Synergistic Effect of V/S Co-Doping on Boosting the Conductivity and Stability of LiMn0.6Fe0.4PO4 Cathodes for Lithium-Ion Batteries

Jinrui Liang,Yongqian Han,Yinghong Wang,Xiaofeng Liu,Qiaoli Zhang,Abdul Hameed Pato,Longtao Ren,Wen Liu

Lithium manganese iron phosphate (LMFP) is considered a promising cathode material for next-generation lithium-ion batteries due to its high operating voltage and enhanced energy density compared to lithium iron phosphate (LFP). However, its commercial viability is hindered by poor intrinsic electronic conductivity and rapid capacity fade caused by Jahn–Teller distortion. Herein, we propose a strategy of vanadium and sulfur co-doping to fabricate a carbon-coated LiMn0.6Fe0.4PO4 cathode material (VS-LMFP) via a scalable solid-state synthesis. Rietveld refinement of X-ray diffraction patterns and advanced microscopy techniques confirm that V and S are successfully incorporated into the crystal lattice without forming secondary phases, inducing subtle structural modifications. Density functional theory calculations reveal that this co-doping reduces the band gap from 0.51 to 0.4 eV, significantly enhancing the intrinsic electronic conductivity. The resulting VS-LMFP cathode exhibits an excellent initial discharge capacity of 156.7 mAh g−1 at 0.1 C and maintains 125 mAh g−1 after 600 cycles at 1 C, demonstrating superior rate capability and cycling stability. The enhanced performance is attributed to the synergistic effect of V and S co-doping, which improves Li+ diffusion kinetics, stabilizes the structure against Jahn–Teller distortion, and reduces charge transfer resistance. This work provides a fundamental insight into the mechanism of co-doping and offers an effective pathway for the rational design of high-energy-density, durable cathode materials.

Synergistic structural stabilization and interface engineering of LiMn0.6Fe0.4PO4 cathodes via Nb5+ doping and second-time carbon coating for lithium-ion batteries

Chao Ye,Wenqin Ling,Xiaowei Huang,Yao Wu,Naigen Zhou,Xuerui Yang

Olivine-structured LiMn x Fe 1-x PO 4 (LMFP) has garnered significant attention as a cathode material for lithium-ion batteries (LIBs) due to its high energy density and low cost. However, its widespread application is limited by its inherently low electronic and ionic conductivities, as well as structural instability arising from the Jahn-Teller distortion of Mn 3+ ions and interfacial side reactions. To address these challenges, this study developed an innovative synergistic modification strategy combining Nb 5+ doping with second-time carbon coating to prepare high-performance LiMn 0.6 Fe 0.4 PO 4 /C cathode materials. Nb 5+ doping stabilizes the crystal structure during cycling by strengthening M-O bonding interactions, thus effectively alleviating the Jahn-Teller distortion of Mn 3+ . Meanwhile, uniform carbon coating layer effectively suppresses electrolyte attack on the material and mitigates Mn dissolution. Furthermore, the synergistic effects of Nb 5+ doping and second-time carbon coating significantly enhance the Li + /e − transport efficiency of the material by narrowing the band gap and constructing a continuous conductive network. As a result, the dual-modified LMFP/DC-2Nb electrode exhibits significantly enhanced cycling stability and rate capability, delivering an initial discharge capacity of 158.3 mAh g −1 at 0.1 C and achieving 93.2 % capacity retention at 1 C after 700 cycles. Moreover, a high specific capacity of 156.2 mAh g −1 is delivered after 200 cycles at 1 C and 50 °C with negligible capacity fading, and a discharge capacity of 119.8 mAh g −1 is maintained even at a high rate of 5 C. The synergistic modification strategy holds great potential for application and offers broad prospects for the design and development of high-energy-density, low-cost, and high-performance lithium-ion batteries.

Economical and efficient synthesis of a uniform LiMn0.6Fe0.4PO4/C cathode for lithium ion batteries via a manganese iron spinel oxide precursor

Zhongdong Peng,Xinghuo Luo,Jiahui Wu,Tingting Yi,Guorong Hu,Yanbing Cao,Ke Du

Manganese-rich olivine phosphates (LiMn y Fe 1-y PO 4 , y > 0.5) are promising as cathodes for lithium ion batteries due to their high energy density and good safety. However, the sluggish kinetics of the Mn 2+ /Mn 3+ redox reaction and inherently low conductivity have impeded the full utilization of their performance. The uniform distribution of transition metal ions is an effective strategy for high performance LiMn y Fe 1-y PO 4 cathode. In this study, leveraging the analogous crystal structures of manganese and iron spinel oxides , we introduce a novel Mn 1.8 Fe 1.2 O 4 precursor. This precursor facilitates the formation of a solid solution phase material with uniform manganese and iron distributions through a chemical coprecipitation method. When employed in the fabrication of LiMn 0.6 Fe 0.4 PO 4 /C composites, improved kinetic conditions for electrochemical reactions due to consistent phase composition, this approach yields an impressive energy density of 593 Wh kg −1 at 0.1C with a middle voltage (3.93 V), 149.8 mAh g −1 at 1C, a superior rate capability of 132.5 mAh g −1 at 10C, and a remarkable capacity retention of 96.5 % after 300 cycles at 1C. Techno-economic analyses further demonstrate that this method offers significant economic and environmental benefits, owing to high material utilization efficiency, minimized emissions, and energy savings. The oxide coprecipitation process presents a sustainable pathway for the industrial-scale synthesis of LiMn y Fe 1-y PO₄ cathodes and potentially extends to other advanced cathodes in high performance lithium ion batteries.