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<p>Currently, lithium-ion batteries (LIBs) are playing an increasingly important role in the energy and power sector, powering electric vehicles, energy storage devices, robots, and electronic devices. As a component of LIBs, the binder also plays a crucial role in the charge/discharge performance, energy density, and stability of the battery. Although conventional PVDF possesses outstanding electrochemical stability, it suffers from high cost, moisture sensitivity, fluorine pollution, and poor adhesion. Moreover, because PVDF is dissolved in the organic solvent N-methyl-2-pyrrolidone (NMP), the solvent evaporation process poses environmental and safety risks such as air pollution and fire hazards. To address these issues, this work proposes an environmentally friendly and safe water-soluble electrode binder—high-molecular-weight polyvinyl alcohol (PVA) with an average degree of polymerization of 2400 and a degree of alcoholysis of 88% for lithium iron phosphate (LFP) cathode. Solubility theory analysis verified that this binder does not dissolve or swell in the lithium battery electrolyte, and density functional theory (DFT) simulations confirmed its electrochemical stability. Raman spectroscopy determined the molecular structure of the binder, and adhesion energy calculations together with tape tests confirmed its superior adhesion. The diffusion coefficients of lithium ions in half-cells using the two binders (high-molecular-weight PVA and PVDF), investigated by cyclic voltammetry (CV) and galvanostatic intermittent titration technique (GITT), were 10<sup>−13</sup> and 10<sup>−14</sup> order of magnitudes. According to cycling charge/discharge tests, the rate capacity and capacity retention values of the half-cell using PVA binder were both better than that of half-cell using PVDF binder. Subsequently, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were employed to investigate the electrochemical mechanisms, elemental states on the electrode surface, and surface micro-morphologies of the two half-cells before and after cycling. The experimental results demonstrate that the cathode with the high-molecular-weight PVA binder exhibits a more uniform electrode surface, greater adhesion strength, faster lithium-ion diffusion, superior rate capability, and higher capacity retention.</p>

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Study on the electrochemical properties of a water-based binder for lithium iron phosphate cathode

  • 期刊论文

  • 发表日期：

    2026年7月23日

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  • Yangshuhan Xu

摘要

Currently, lithium-ion batteries (LIBs) are playing an increasingly important role in the energy and power sector, powering electric vehicles, energy storage devices, robots, and electronic devices. As a component of LIBs, the binder also plays a crucial role in the charge/discharge performance, energy density, and stability of the battery. Although conventional PVDF possesses outstanding electrochemical stability, it suffers from high cost, moisture sensitivity, fluorine pollution, and poor adhesion. Moreover, because PVDF is dissolved in the organic solvent N-methyl-2-pyrrolidone (NMP), the solvent evaporation process poses environmental and safety risks such as air pollution and fire hazards. To address these issues, this work proposes an environmentally friendly and safe water-soluble electrode binder—high-molecular-weight polyvinyl alcohol (PVA) with an average degree of polymerization of 2400 and a degree of alcoholysis of 88% for lithium iron phosphate (LFP) cathode. Solubility theory analysis verified that this binder does not dissolve or swell in the lithium battery electrolyte, and density functional theory (DFT) simulations confirmed its electrochemical stability. Raman spectroscopy determined the molecular structure of the binder, and adhesion energy calculations together with tape tests confirmed its superior adhesion. The diffusion coefficients of lithium ions in half-cells using the two binders (high-molecular-weight PVA and PVDF), investigated by cyclic voltammetry (CV) and galvanostatic intermittent titration technique (GITT), were 10−13 and 10−14 order of magnitudes. According to cycling charge/discharge tests, the rate capacity and capacity retention values of the half-cell using PVA binder were both better than that of half-cell using PVDF binder. Subsequently, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were employed to investigate the electrochemical mechanisms, elemental states on the electrode surface, and surface micro-morphologies of the two half-cells before and after cycling. The experimental results demonstrate that the cathode with the high-molecular-weight PVA binder exhibits a more uniform electrode surface, greater adhesion strength, faster lithium-ion diffusion, superior rate capability, and higher capacity retention.