MOF-Derived Carbon-Anchored Cu₂Se/MnSe Heterointerfacial Nanoparticles for Enhanced Lithium Storage via Synergistic Interface Effects

Abstract

To address the inherent limitations of Cu₂Se as a lithium-ion battery (LIB) anode, a Cu₂Se/MnSe@C composite was rationally designed and synthesized via selenization of a CuMn bimetallic metal–organic framework (MOF) precursor. This synthesis strategy integrates carbon composite engineering and heterogeneous structure construction, achieving in situ formation of Cu₂Se/MnSe heterogeneous nanoparticles anchored on amorphous carbon nanosheets. Structural characterizations confirm the successful construction of well-defined Cu₂Se/MnSe interfaces and uniform dispersion of selenide components, with Mn introduction inducing regulated electron transfer between Cu₂Se and MnSe. Electrochemical evaluations demonstrate that the Cu₂Se/MnSe@C composite exhibits a significantly enhanced lithium storage performance compared to single-component Cu₂Se@C, including higher specific capacity and superior rate capability. Mechanistic studies reveal that the synergistic effects of the carbon matrix (enhancing electrical conductivity and mitigating volume expansion) and the Cu₂Se/MnSe heterogeneous interface (lowering charge transfer resistance, accelerating Li⁺ diffusion, and boosting pseudocapacitive contribution) are responsible for the performance enhancement. Moreover, Cu₂Se/MnSe@C||LiFePO₄ full cells deliver a stable average operating voltage and reliable cycling stability, validating the composite’s practical application potential.

1. Introduction

As a core component of lithium-ion batteries (LIBs), the anode material directly determines the battery’s overall electrochemical performance. Among various candidate anode materials, transition metal selenides (TMSes) have attracted considerable attention due to their higher theoretical specific capacities, better electrical conductivity, and more favorable redox kinetics compared to traditional graphite [1,2,3]. Copper selenide (Cu₂Se) stands out as a promising candidate owing to its abundant reserves, low cost, and moderate volume expansion during lithiation/delithiation processes [4,5]. However, Pure Cu₂Se has inherent drawbacks of structural pulverization during cycling and sluggish ion/electron transfer kinetics, and single modification strategies fail to address these issues comprehensively [6,7,8].

Carbon hybridization alone can enhance conductivity and alleviate volume expansion but cannot modulate the intrinsic electronic structure of Cu₂Se [9]. Heterogeneous interface construction solely optimizes charge distribution yet lacks a robust carbon scaffold to avoid interfacial collapse [10,11]. Thus, the synergistic combination of the two strategies is a rational design, which realizes dual optimization of structural stability and electrochemical kinetics for Cu₂Se-based anodes, with the carbon matrix acting as a stable conductive support for heterointerfaces and the heterointerfaces boosting ion/charge transfer efficiency [12,13]. Manganese selenide (MnSe) is rationally selected as the secondary selenide component for its multiple synergistic characteristics with Cu₂Se: it has a favorable lattice matching degree for the formation of stable Cu₂Se/MnSe heterointerfaces, complementary redox behavior and high theoretical capacity to increase lithium storage active sites and total specific capacity, and the unique atomic properties of Mn that induce effective charge transfer between Cu₂Se and MnSe, thus modulating the electronic structure and lowering the charge transfer resistance of the composite [14,15,16].

In this work, we rationally designed and synthesized a Cu₂Se/MnSe@C composite anode by integrating carbon composite and heterogeneous structure construction strategies. The composite was fabricated via selenization of a CuMn bimetallic metal–organic framework (MOF) precursor, enabling in situ formation of Cu₂Se/MnSe heterogeneous nanoparticles anchored on amorphous carbon nanosheets. Structural and compositional characterizations confirmed the successful construction of well-defined Cu₂Se-MnSe heterogeneous interfaces and uniform dispersion of selenide components on the carbon matrix, accompanied by regulated electron transfer between Cu₂Se and MnSe induced by Mn introduction. Electrochemical evaluations demonstrated that the Cu₂Se/MnSe@C composite outperformed single-component Cu₂Se@C in specific capacity, rate capability, and cycling stability. Mechanistic analyses revealed that the enhanced performance originated from the synergistic effects of the carbon matrix (reinforcing conductivity and structural integrity) and the heterogeneous interface (lowering charge transfer resistance, accelerating Li⁺ diffusion, and boosting pseudocapacitive contribution). Moreover, the assembly of Cu₂Se/MnSe@C||LiFePO₄ full cells validated the composite’s practical application potential, delivering stable operating voltage and long-cycle reliability.

2. Results and Discussion

The phase composition of the selenized products derived from Cu-MOF and CuMn-MOF was characterized via X-ray diffraction (XRD) characterization. As illustrated in the XRD pattern (Figure 1a), selenization of Cu-MOF yielded single-phase Cu₂Se (PDF No. 29-0575), whereas selenized CuMn-MOF produced a Cu₂Se/MnSe binary composite (PDF No. 29-0575 and PDF No. 75-0889). As illustrated in Figure S1 and Figure 1b, the scanning electron microscope (SEM) images reveal that the composite is constructed by the assembly of nanosheets, with ultra-small nanoparticles uniformly anchored on the surface of the nanosheets. Transmission electron microscope (TEM) characterization (Figure 1c) further confirms the homogeneous dispersion of these nanoparticles onto the amorphous carbon nanosheet, forming a well-integrated hybrid structure. High-resolution TEM (HRTEM) images (Figure 1d,e) demonstrate the presence of distinct heterogeneous interfaces between Cu₂Se and MnSe. These well-defined heterogeneous interfaces play a pivotal role in enhancing the lithium storage performance of the composite: firstly, they can modulate the electronic structure and optimize the charge distribution at the interface, thereby reducing the energy barrier for lithium ion diffusion and accelerating charge transfer kinetics [17,18]; secondly, the synergistic interaction between Cu₂Se and MnSe across the interface alleviates the volume expansion during repeated lithiation/delithiation cycles, improving the structural stability of the composite [19]; additionally, the interface provides abundant active sites for lithium ion adsorption and redox reactions, which contributes to the enhancement of lithium storage capacity [20]. Furthermore, selected area electron diffraction (SAED) patterns exhibit characteristic diffraction rings corresponding to the crystal planes of Cu₂Se and MnSe (Figure 1f), which further confirms the successful fabrication of the heterogeneous structure in the Cu₂Se/MnSe@NC composite.

X-ray photoelectron spectroscopy (XPS) measurements were performed to investigate the elemental composition and chemical states of the Cu₂Se@C and Cu₂Se/MnSe@C composites. As presented in the survey XPS spectrum (Figure 2a), both composites contain Cu, Se, C, and O elements, which confirms the successful retention of the main components during the synthesis process. Notably, an additional characteristic peak corresponding to Mn is detected in the Mn 2p spectrum of Cu₂Se/MnSe@C (Figure 2b), verifying the successful introduction of Mn into the bimetallic selenide composite without the presence of unexpected impurities [21]. As exhibited in Figure 2c,d, the Cu 2p and Se 3d spectra of Cu₂Se/MnSe@C show distinct negative shifts with quantifiable values compared to those of Cu₂Se@C after the introduction of Mn: the Cu 2p_3/2 peak presents a negative shift of ~0.1 eV, and the Se 3d_3/2 peak exhibits a negative shift of ~0.4 eV. This characteristic binding energy shift directly indicates that both Cu and Se atoms gain electrons [22,23], which is attributed to the redistribution of interfacial electron cloud density induced by the formation of Cu₂Se/MnSe heterogeneous interfaces; the electronegativity difference between Mn and Cu/Se triggers the transfer of partial electron density from Mn to the Cu₂Se phase across the heterointerface [24], thus increasing the electron occupancy of Cu and Se atomic orbitals. In addition, the reduced intensity of Cu 2p satellite peaks in Cu₂Se/MnSe@C relative to Cu₂Se@C is attributed to the modulation of Cu valence state by interfacial electronic interaction: Mn introduction induces directional charge transfer between Cu₂Se and MnSe, where Cu atoms gain electrons and partial Cu²⁺ is reduced to lower-valence Cu⁺ species [25], which directly leads to the weakened satellite peak intensity. This interface-induced Cu valence modulation optimizes the surface electronic structure of the composite by reducing the energy barrier for charge transfer at the electrode–electrolyte interface and increasing the active sites for Li⁺ adsorption, effectively facilitating charge transfer kinetics and thus enhancing lithium storage performance. The C 1s spectra of both Cu₂Se@C and Cu₂Se/MnSe@C were deconvoluted into three characteristic peaks (Figure 2e), corresponding to the C-C, C-O, and C=O bonds, respectively [26]. The O 1s spectra (Figure 2f) of Cu₂Se@C and Cu₂Se/MnSe@C are deconvoluted into three labeled components: O_latt (lattice oxygen), O_ads (adsorbed oxygen), and O_w (water). O_latt corresponds to metal-oxygen (M-O) bonds on Cu₂Se/MnSe nanoparticle surfaces, O_ads to surface-adsorbed oxygen and oxygen-containing functional groups in the carbon matrix, and O_w to physically adsorbed water molecules [27,28]. Overall, the XPS analysis not only verifies the desired elemental composition of the composites but also reveals the quantitative characteristics and mechanism of the electronic interaction induced by Mn introduction: Mn triggers directional charge transfer and electron cloud redistribution at the Cu₂Se/MnSe heterointerface, modulates the valence state of Cu species and the electron density of Se atoms, and optimizes the surface electronic structure of the composite. These interfacial electronic regulation effects are conducive to reducing the charge transfer resistance, accelerating Li⁺ diffusion kinetics, and increasing the active sites for lithium storage, thus comprehensively enhancing the electrochemical performance of the composite in lithium storage applications.

As exhibited in the cyclic voltammetry (CV) curves (Figure 3a,b and Figure S2), Cu₂Se@C shows two pairs of redox peaks (R1/R2 for reduction, O1/O2 for oxidation), corresponding to the stepwise conversion of Cu₂Se to Cu and Li₂Se via a CuSe intermediate [29]. In contrast, Cu₂Se/MnSe@C presents an additional redox pair (R3/O3) derived from MnSe’s characteristic conversion reaction [30], contributing extra lithium storage capacity. Moreover, the CV curves of Cu₂Se/MnSe@C from the second to the fourth cycle are nearly overlapping, demonstrating superior electrochemical reversibility compared to Cu₂Se@C, which benefits from the synergistic stabilization of the heterogeneous interface and carbon matrix. The rate capability test (Figure 3c) further confirms that Cu₂Se/MnSe@C outperforms Cu₂Se@C. Even at high current densities, Cu₂Se/MnSe@C maintains a significantly higher specific capacity (Figure 3d). The morphological and microstructural features of Cu₂Se/MnSe@C revealed by SEM and TEM are the key structural bases for its enhanced electrochemical performance. The carbon nanosheet-assembled framework provides a continuous conductive network for fast electron transport and a flexible buffer to mitigate volume expansion during cycling; the uniformly anchored ultra-small Cu₂Se/MnSe nanoparticles enlarge the electrode–electrolyte contact area and increase lithium storage active sites with shortened ion diffusion distance; the well-defined heterointerfaces on carbon nanosheets accelerate interfacial charge transfer and maintain structural integrity upon cycling. These structural merits synergistically optimize the composite’s electrochemical kinetics and structural stability, thus leading to its higher specific capacity and superior rate capability than Cu₂Se@C. XPS analysis indicates that the surface atomic percentages (at%) are C: 73.88%, Se: 3.78%, O: 19.48%, Cu: 2.86% for Cu₂Se@C, and C: 72.73%, Se: 4.61%, O: 19.87%, Mn: 2.30%, Cu: 0.50% for Cu₂Se/MnSe@C. After conversion, the mass percentages (wt%) of carbon in Cu₂Se@C and Cu₂Se/MnSe@C materials are 53% and 51%, respectively. The trade-off between carbon content and initial coulombic efficiency (ICE) is critical for carbon-based anodes, as high-surface-area carbon easily causes excessive electrolyte decomposition and thick SEI film formation, leading to irreversible Li⁺ loss and reduced ICE. The carbon contents of Cu₂Se@C and Cu₂Se/MnSe@C are 53% and 51% respectively, at a moderate level. The tight anchoring of selenide nanoparticles on amorphous carbon nanosheets reduces the exposed active surface of the carbon matrix, which not only maintains the carbon’s roles in improving electrical conductivity and alleviating volume expansion during lithiation/delithiation, but also inhibits excessive SEI formation effectively. This design realizes a favorable balance between carbon content and ICE, and the better ICE performance of Cu₂Se/MnSe@C with lower carbon content further confirms the rationality of carbon content regulation in this work. Additionally, Cu₂Se/MnSe@C exhibits a capacity increase during long-term cycling at 1 A g⁻¹ (Figure 3e), which may be associated with its structural advantages. Repeated lithiation/delithiation is likely to promote electrolyte infiltration into the carbon matrix, thus gradually activating the latent inner active sites of Cu₂Se/MnSe nanoparticles and increasing the effective sites for lithium storage [31]. Moreover, the flexible carbon matrix alleviates the volume change of selenide nanoparticles; the tiny pores generated in cycling may serve as extra Li⁺ diffusion channels, and the contact between active nanoparticles may be tightened upon cycling, which could optimize the electronic conduction network and improve ion/electron transport efficiency [32]. The combined effect of these factors may lead to the capacity increase, indirectly verifying the good structural stability of Cu₂Se/MnSe@C during long-term cycling.

CV tests were conducted on Cu₂Se@C and Cu₂Se/MnSe@C composites to probe the lithium storage mechanism and pseudocapacitive contribution (Figure S3 and Figure 4a). As depicted in Figure 4b, the log(i) vs. log(v) plots were employed to calculate the slope (b-value), a key parameter reflecting the charge storage behavior—where a b-value of ~0.5 indicates diffusion-controlled intercalation/deintercalation, and a value of ~1.0 corresponds to surface-dominated pseudocapacitive behavior [33,34]. The Cu₂Se/MnSe@C composite exhibits a higher b-value (0.58) compared to Cu₂Se@C (0.42), suggesting that the introduction of MnSe modulates the lithium storage mechanism by enhancing the pseudocapacitive contribution. This higher b-value implies faster charge transfer kinetics and Li⁺ diffusion efficiency, as pseudocapacitive reactions are less dependent on ion diffusion within the bulk material and instead occur rapidly at the electrode–electrolyte interface [35,36]. Furthermore, the pseudocapacitive contribution ratios of the two composites were quantitatively analyzed. The k₁ (capacitive) and k₂ (diffusion-controlled) values were calculated using the classic equation i = k₁v + k₂v^1/2: peak currents at characteristic potentials were extracted from CV curves (0.2–1.6 mV s⁻¹), a linear fit of i/v^1/2 vs. v^1/2 was performed at each potential, yielding the slope (k₁) and intercept (k₂). At all tested scan rates, Cu₂Se/MnSe@C demonstrates a higher pseudocapacitive proportion than Cu₂Se@C (Figure 4c, Figures S4 and S5). The elevated pseudocapacitive contribution not only explains the superior rate capability of Cu₂Se/MnSe@C but also contributes to its enhanced cycling stability. Pseudocapacitive reactions mitigate the structural strain caused by repeated ion insertion/extraction, as they involve minimal volume change compared to diffusion-controlled processes [37]. Additionally, the increased pseudocapacitive behavior is closely associated with the heterogeneous interface between Cu₂Se and MnSe, which creates abundant active sites for surface redox reactions and optimizes the electronic structure to facilitate rapid charge transfer [38]. Collectively, these results confirm that the integration of MnSe into Cu₂Se@C promotes a transition toward pseudocapacitive-dominated lithium storage, endowing the composite with improved electrochemical kinetics and overall performance.

To quantitatively analyze electrochemical kinetics and interfacial behaviors, an equivalent circuit model was used to fit the Nyquist plots (Figure 4d). Herein, R_s denotes solution and contact resistance, R_ct is interfacial charge transfer resistance, CPE compensates for non-ideal double-layer capacitance, and W_o characterizes Li⁺ diffusion within the electrode [39,40]. Fitting results show that Cu₂Se/MnSe@C has smaller R_s (12 Ω vs. 83 Ω) and R_ct (581 Ω vs. 1120 Ω) compared to Cu₂Se@C, indicating the heterogeneous structure and carbon matrix synergistically optimize interface contact and reduce charge transfer barriers. This reduction in R_s and R_ct originates from two key structural advantages: first, the amorphous carbon matrix forms a continuous conductive network that minimizes the contact resistance between active particles and the current collector, accounting for the lower R_s [41]; second, the electronic interaction at the Cu₂Se/MnSe heterointerface redistributes the electron cloud density, reduces the energy barrier for charge transfer across the electrode–electrolyte interface, and thus drastically lowers R_ct [42]. Furthermore, the linear portion of the electrochemical impedance spectroscopy (EIS) plots reflects the Li⁺ diffusion process within the electrode materials. The Cu₂Se/MnSe@C composite shows a much lower slope of the linear segment (Figure 4e), suggesting a faster Li⁺ diffusion rate in the bimetallic selenide composite [43]. This accelerated Li⁺ diffusion can be attributed to the synergistic effects of the heterogeneous structure and the carbon matrix: in addition to the short-range diffusion pathways provided by the well-defined Cu₂Se/MnSe interfaces, the heterointerface-induced lattice distortion at the interfacial boundaries in the selenide phases creates abundant interstitial channels for Li⁺ migration, while the porous carbon framework acts as a fast ion transport medium that shortens the diffusion distance of Li⁺ from the electrolyte to the active material surface. The galvanostatic intermittent titration technique (GITT) tests (Figure 4f–i) further corroborated the superior ion diffusion kinetics of Cu₂Se/MnSe@C. The GITT-derived Li⁺ diffusion coefficients during both lithiation and delithiation processes are higher for Cu₂Se/MnSe@C than for Cu₂Se@C. Specifically, the D(Li⁺) values of Cu₂Se/MnSe@C remain stable across different charge–discharge states, indicating consistent and rapid Li⁺ transport throughout the cycling process. This stability in D(Li⁺) is attributed to the structural robustness of the composite: the carbon matrix buffers the volume expansion of selenides during cycling, while the strong interaction at the Cu₂Se/MnSe heterointerface prevents the disintegration of active phases, thus maintaining the integrity of Li⁺ diffusion pathways over repeated cycles. In contrast, Cu₂Se@C exhibits lower and more fluctuating D(Li⁺) values, reflecting limited ion diffusion efficiency caused by severe volume expansion and the lack of interfacial diffusion channels. Collectively, the EIS and GITT results demonstrate that the Cu₂Se/MnSe@C composite possesses enhanced charge transfer kinetics and accelerated Li⁺ diffusion compared to Cu₂Se@C. These favorable electrochemical kinetics are closely associated with the unique heterogeneous structure and the synergistic interaction between Cu₂Se, MnSe, and the carbon matrix: the electronic modulation at the heterointerface optimizes charge transfer, the interfacial boundaries create fast Li⁺ diffusion channels, and the carbon matrix ensures structural stability and continuous ion/electron transport—all contributing to the composite’s excellent rate capability and cycling stability observed in previous electrochemical tests.

To further explore the practical application potential of the Cu₂Se/MnSe@C composite as an anode material, coin-type full cells were assembled and characterized. As schematically illustrated in Figure 5a, the full cell configuration employs Cu₂Se/MnSe@C as the anode and lithium iron phosphate (LFP, Figure S6) as the cathode. The rate capability of the Cu₂Se/MnSe@C||LFP full cell was evaluated at various current densities, as presented in Figure 5b. In addition, the Cu₂Se/MnSe@C||LFP full cell exhibits an average operating voltage of ~2.7 V (Figure 5c), which is compatible with commercial LIB requirements. A visual demonstration of the full cell powering light-emitting diodes (LEDs, Figure 5d) further verifies its practical electrochemical output capability. The Cu₂Se/MnSe@C||LFP full cell demonstrates favorable cycling stability (Figure 5e), maintaining a stable specific capacity over long-term charge–discharge cycles. Collectively, the Cu₂Se/MnSe@C||LFP full cell demonstrates prominent rate capability, a stable operating voltage, and superior long-cycle stability, coupled with successful LED lighting performance.

3. Experimental Section

3.1. Synthesis of CuMn-MOF Precursor

The CuMn-MOF precursor was synthesized via a hydrothermal method. Typically, 0.75 mmol Cu(NO₃)₂·3H₂O and 0.75 mmol Mn(NO₃)₂·4H₂O were dissolved in 20 mL ethanol. Subsequently, 1.0 g polyvinylpyrrolidone was added to the solution, which was then stirred continuously for 30 min to form a homogeneous mixture denoted as Solution A. Meanwhile, 0.2 mmol terephthalic acid was dissolved in 20 mL N,N-dimethylformamide with vigorous stirring to prepare Solution B. Solution B was slowly added dropwise into Solution A over a period of 30 min under constant stirring to ensure uniform mixing. The resulting mixture was transferred into a 100 mL Teflon-lined stainless-steel autoclave, sealed tightly, and subjected to hydrothermal reaction at 120 °C for 24 h. After the reaction system was naturally cooled to room temperature, the solid product was collected by centrifugation at 10,000 rpm (revolutions per minute), washed thoroughly with ethanol three times to remove residual impurities, and then vacuum-dried at 60 °C for 12 h to obtain the CuMn-MOF precursor. For the control sample (Cu-MOF), it was synthesized under identical experimental conditions except that 1.5 mmol Cu(NO₃)₂·3H₂O was used as the sole metal source instead of the CuMn bimetallic nitrate mixture.

3.2. Synthesis of Cu₂Se/MnSe@C Composite

The Cu₂Se/MnSe@C composite was prepared by gas-phase selenization of the CuMn-MOF precursor. A quartz boat containing 100 mg selenium powder was placed upstream in a tube furnace, and 200 mg of the CuMn-MOF precursor was placed in a separate crucible downstream. Under a continuous argon flow rate of 50 sccm (standard cubic centimeters per minute) to maintain an inert atmosphere, the system was heated at a rate of 5 °C min⁻¹ to 650 °C and held at this temperature for 2 h to ensure full selenization. After the reaction, the product was furnace-cooled to room temperature under argon protection and collected as the Cu₂Se/MnSe@C composite. The pure Cu-MOF precursor was selenized under the same conditions to obtain the Cu₂Se@C sample.

3.3. Characterization

Powder X-ray diffraction (XRD, Shimadzu XRD-6100 (Shimadzu Corporation, Kyoto, Japan), Cu Kα, λ = 1.5418 Å, 40 kV) characterized crystallographic structures over 2θ = 10–80° (5° min⁻¹). Morphology and microstructure were observed via SEM (Zeiss Gemini 500 (Carl Zeiss AG, Oberkochen, Germany), 20 kV) and TEM (FEI Tecnai G2 F30 (FEI Company, Hillsboro, OR, USA), 200 kV). Surface chemical states and elemental valence were analyzed by XPS (Thermo Fisher K-Alpha (Thermo Fisher Scientific, Waltham, MA, USA), Al Kα, 1486.6 eV), with the powder samples fixed on the sample stage using conductive adhesive and all XPS spectra calibrated for energy accuracy against the standard binding energy of C 1s = 284.8 eV.

3.4. Electrochemical Measurements

Working electrodes were fabricated by mixing the active material, acetylene black (conductive agent), and polyvinylidene fluoride (PVDF, binder) in a mass ratio of 7:2:1. The mixture was dispersed in N-methyl-2-pyrrolidone to form a homogeneous slurry, which was uniformly cast on Cu foil. The coated Cu foil was vacuum-dried at 60 °C for 12 h, and the thickness of the active material layer was controlled at 100 microns. After drying, the Cu foil was punched into 12 mm-diameter discs, and the electrode was compacted to ensure sufficient contact between the active material, conductive agent, and current collector. CR2025 coin cells were assembled in an argon-filled glovebox (H₂O/O₂ < 0.01 ppm), using lithium foil as counter/reference electrode, Celgard 2500 as separator, and 1 M LiPF₆ in EC/DEC/EMC (1:1:1 v/v) as electrolyte. Galvanostatic charge–discharge tests were conducted on a NEWARE BST-60 system within 0.01–3.0 V (vs. Li/Li⁺). EIS measurements were performed on a CHI760E workstation in the frequency range of 0.1 Hz to 100 kHz with an AC amplitude of 5 mV at the open circuit potential. GITT tests were conducted on a NEWARE BST-60 system at a current density of 50 mA g⁻¹, with a pulse duration of 0.5 h and a relaxation time of 4 h, within the voltage window of 0.01–3.0 V (vs. Li/Li⁺).

4. Conclusions

In summary, a Cu₂Se/MnSe@C composite anode material with integrated carbon hybridization and heterogeneous interface engineering was successfully fabricated via MOF-derived selenization. The key innovation lies in the rational combination of Cu₂Se and MnSe to form well-defined heterogeneous interfaces, coupled with in situ growth on carbon nanosheets, which synergistically addresses the intrinsic drawbacks of pure Cu₂Se. Structural and compositional analyses confirm that Mn introduction modulates the electronic interaction between Cu₂Se and MnSe, while the carbon matrix ensures structural integrity and rapid electron transport. Electrochemical and mechanistic studies validate that the heterogeneous interfaces not only reduce charge transfer resistance and accelerate Li⁺ diffusion but also enhance pseudocapacitive contribution, thereby promoting overall electrochemical kinetics. As a result, the Cu₂Se/MnSe@C composite outperforms Cu₂Se@C in specific capacity and rate capability. Furthermore, the successful assembly of full cells with LiFePO₄ cathodes demonstrates the composite’s practical applicability.