Composite Hybrid Materials Based on Transition Metal Compounds and Conducting Polymers for Lithium-Ion Batteries: Role of Binders and Polymer Conductivity in Material Performance

Grant Number: 14-29-04043

Project Description

The project targets the synthesis, structural study, and electrochemical characterization of core–shell hybrid nanocomposite materials based on transition metal compounds and conducting polymers, and the assessment of their functionality as lithium-ion battery (LIB) electrode materials.

Main objective:
Enhance the energy, power, and cycling performance of inorganic cathode materials (LiFePO₄, LiFe₀.₅Mn₀.₅PO₄, LiMn₂O₄, etc.) by forming core–shell hybrid nanocomposites with conducting polymers:

Poly(3,4-ethylenedioxythiophene) (PEDOT)
Colloidal dispersion PEDOT:PSS (poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate)

Rationale and approach:

Using conducting polymer as both conductive additive and binder (replacing or partially substituting traditional components) increases the mass fraction of active material, thus raising electrode specific capacity.
Nanostructuring and surface modification of ultrafine active particles with a conducting additive/polymer promotes fast Li-ion (de)insertion, boosting power.
Polymer coatings on active grains mitigate solvent interaction and electrochemical dissolution during cycling, reducing degradation and acting as a stabilizing layer without hindering Li-ion transport.

The strategy emphasizes developing original synthesis routes to hybrid nanoparticles with predefined structure, component composition, and electronic state, as next-generation LIB electrode materials with increased specific power.

A broad suite of techniques will be used to determine structure and functional electrochemical characteristics:

X-ray diffraction (XRD)
AFM and electron microscopy
IR and Raman spectroscopy
Cyclic voltammetry, chronopotentiometry, impedance spectroscopy, etc.

The interdisciplinary project will produce nanostructured hybrid materials, elucidate their structure and electrochemistry, and define which formulation—conducting polymer additive, carbon additive, or their combination—delivers optimal performance.

Project Report

Key results:

Studied new LIB cathode materials based on LFP (LiFePO₄), LFMP (LiFe₀.₄Mn₀.₆PO₄), LMO (LiMn₂O₄), incorporating PEDOT as a PEDOT:PSS dispersion combined with carboxymethyl cellulose (CMC).
- For LFP and LFMP, the effect of binder type (latex LA-133, CMC, PEDOT:PSS dispersion) on functional properties was examined in detail, varying ratios of polymer additives and carbon black.
- Optimized cathode compositions using the promising conductive binder system PEDOT:PSS/CMC.
Electrochemical properties of LFP/PEDOT:PSS/CMC, LFMP/PEDOT:PSS/CMC, MnO₂/PEDOT:PSS/CMC, and LMO/PEDOT:PSS/CMC were characterized by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy.
- Obtained specific capacity, its rate dependence (0.2–20 C), and cycling life.
- In all cases, introducing conducting polymer modifiers yielded a 15–20% increase in specific capacity while simultaneously increasing the active material fraction.
Impedance spectroscopy was used to systematically study charge–discharge kinetics for the most promising LFP, LFMP, LMO cathode materials.
- Quantified charge transfer resistance and effective Li-ion diffusion coefficients across compositions and potentials, comparing to PVDF-based standards.
- For LFP and LFMP modified with conducting polymers, interfacial charge transfer resistance decreased 5–10×, and effective Li-ion diffusion coefficients increased by over an order of magnitude.
- For LMO/PEDOT:PSS/CMC, polymer modification also accelerated charge–discharge via higher diffusion coefficients and lower interfacial resistance.
- Polymer shell coatings on LMO grains improved capacity stability during long-term cycling.
XRD on representative samples (LFP/PEDOT:PSS/CMC, LFMP/PEDOT:PSS/CMC, LMO/PEDOT:PSS/CMC) showed retention of the olivine-type orthorhombic structure for lithium metal phosphates and the spinel structure for manganese oxide within the composites.
- XPS revealed SEI formation and composition on material surfaces.
- SEM established active particle sizes and distributions, and confirmed polymer shell formation on active grains (core–shell structures).
The project yielded RF Patent No. 2584678 “Composite cathode material for lithium-ion batteries,” plus two patents on methods and devices for producing composites based on conducting polymers and rechargeable transition metal compounds.