Single-Ion Conducting Polymer Electrolytes for Lithium Batteries

Single-ion conducting polymer electrolytes represent a paradigm shift in lithium-battery design by immobilising anionic species within a polymer matrix, thereby allowing only lithium ions to migrate under an electric field. This approach markedly reduces concentration polarisation and mitigates dendrite formation at the lithium metal interface, addressing two of the most persistent barriers to high-energy, safe rechargeable cells. Typical architectures combine a polyelectrolyte backbone—such as polyether, polysulfonylamide or borate-bearing polymers—with tethered anions that provide strong ionic dissociation and high mechanical strength. Optimisation strategies encompass cross-linking, block copolymer design and incorporation of functional fillers or plasticisers to enhance segmental mobility and conductivity at ambient temperature. Advances in microstructure control and interfacial engineering have yielded materials with lithium transference numbers exceeding 0.9, ionic conductivities in the 10⁻⁴–10⁻³ S·cm⁻¹ range and electrochemical stability windows beyond 4.5 V. Beyond laboratory validation in symmetric lithium cells, single-ion polymers are being integrated into full cells with high-voltage cathodes, achieving long cycle life, high coulombic efficiency and improved safety metrics. The global drive towards electric vehicles and grid storage underscores the importance of these materials for next-generation energy storage, with potential deployment in solid-state and hybrid configurations to realise higher energy densities and enhanced operational lifetimes.

Research from Nature Portfolio

Recent studies have demonstrated the preparation of highly porous polybenzimidazole-based separators via a non-solvent induced phase separation process, yielding macroporous membranes with 92 % porosity, electrolyte uptake of 594 wt % and mechanical strength of 15.9 MPa. The electron-rich imidazole rings enhance Li⁺ mobility through electrostatic attraction and suppress PF₆⁻ transport via repulsion, resulting in a lithium transference number of 0.76. In Li/LiFePO₄ cells, these polymer electrolytes exhibit rate capability above 100 mAh g⁻¹ at 6 C and retain stable cycling performance over 1 000 cycles, illustrating the viability of single-ion conduction in practical battery assemblies.

Single-Ion Conducting Polymer Electrolytes for Lithium Batteries publication trend

The graph below shows the total number of articles in single-ion conducting polymer electrolytes for lithium batteries across all publications each year (not limited to Nature Index journals).

Technical terms

Single-ion conducting polymer electrolyte: A polymer network in which fixed anionic sites enable transport exclusively by lithium cations, minimising concentration polarisation.

Lithium transference number: The proportion of total ionic current carried by lithium ions under an applied potential, with values approaching unity in ideal single-ion conductors.

Electrochemical stability window: The voltage range over which an electrolyte remains inert, defining its compatibility with both high-voltage cathodes and lithium metal anodes.

Solid electrolyte interphase (SEI): A passivation layer forming at the lithium surface that regulates ion flux and inhibits continuous electrolyte decomposition.

Dendrite growth: Branch-like lithium deposits that form during cycling, posing a risk of short circuits and capacity loss in metal-based batteries.

References

1. A facile non-solvent induced phase separation process for preparation of highly porous polybenzimidazole separator for lithium metal battery application. Scientific Reports (2019).
2. Accelerated Selective Li+ Transports Assisted by Microcrack‐Free Anionic Network Polymer Membranes for Long Cyclable Lithium Metal Batteries. Advanced Science (2024).
3. Polysiloxane‐Based Single‐Ion Conducting Polymer Blend Electrolyte Comprising Small‐Molecule Organic Carbonates for High‐Energy and High‐Power Lithium‐Metal Batteries. Advanced Energy Materials (2022).
4. Cross-Linking of Sugar-Derived Polyethers and Boronic Acids for Renewable, Self-Healing, and Single-Ion Conducting Organogel Polymer Electrolytes. ACS Applied Energy Materials (2023).