Polymers, due to their inherent flexibility, tunable structures, and ease of functionalization, are expected to address the bottleneck challenges of high energy density batteries.
In this review, Professor Li Zhongtao from China Petroleum University (East China) first analyzes the requirements for cathode, anode, and electrolyte materials in high energy density batteries, as well as the challenges present in current material systems.
Then, the author summarizes and discusses the current status and development trends of polymer materials in these areas. Additionally, the author clarifies the challenges faced by polymer materials in high energy density batteries, including issues related to stability, ion transport, processing, and system integration. Finally, the author outlines the current state and regulatory considerations of polymer materials in high energy density lithium batteries and proposes future development directions in this field. The insights provided are expected to promote the application of polymer materials in lithium batteries and advance the development of high energy density lithium battery technology.
Research Background
Driven by the global transition to a low-carbon and sustainable energy system, high energy density lithium-ion batteries (LIBs) have become the core of next-generation energy storage technologies, providing key momentum for the development of electric vehicles, smart grids, and portable electronic devices. Since their commercialization in 1991, LIBs have gradually replaced traditional lead-acid and nickel-hydride batteries due to their higher energy density, longer cycle life, and lower self-discharge rates. However, as the application fields expand, the limitations of traditional LIB structures have become increasingly prominent, particularly issues such as energy density ceilings, safety hazards, and cost-effectiveness barriers. This technological bottleneck highlights the necessity of developing high specific energy LIB systems, the successful realization of which will have profound impacts on fundamental electrochemical research and industrial energy storage applications.
High energy density LIBs refer to new battery structures that significantly improve energy density, power density, and cycle life compared to traditional LIB systems. This is achieved through the synergistic enhancement of the cathode (high specific capacity, high voltage platform, etc.), anode (high specific capacity, low charge transfer resistance, etc.), and electrolyte (high ionic conductivity, wide electrochemical stability window, etc.). Their core performance indicators include: energy density (targeting 500 Wh/kg for lithium batteries used in electric vehicles by 2030), cycle life (capacity retention rate of no less than 80% after 1000 charge-discharge cycles), temperature adaptability (-60 to 80℃), and safety (through nail penetration tests, suppression of thermal runaway, etc.).
Research Content
Figure 1 Core Performance Indicators of High Energy Density LIBs
This figure illustrates the core performance indicators of the cathode, anode, and electrolyte in high energy density lithium-ion batteries (LIBs). For the cathode, it is required to have high electrochemical stability, excellent ion selectivity, good ion transport capability, and high oxidation resistance, while also suppressing the loss of active materials and interfacial side reactions; for the anode, it must possess high reduction resistance, suppress interfacial side reactions and volume changes; for the electrolyte, it must have high lithium ion transport capability and efficiency, as well as excellent interfacial compatibility. These indicators collectively define the technical boundaries of high specific energy batteries, requiring synergistic optimization of the active materials for the cathode and anode, electrolyte formulations, and interfacial engineering strategies. For example, the combination of high nickel ternary materials with flame-retardant electrolytes can demonstrate safety indicators through nail penetration tests.
Figure 2 Polymer Materials for High Energy Density Lithium-Ion Batteries
This figure illustrates the application scenarios and functions of polymer materials in high energy density lithium-ion batteries. Polymer materials play a key role in the cathode, anode, and electrolyte: in the electrodes, polymers can serve as binders to enhance the bonding of active materials with current collectors, constructing a three-dimensional conductive network; in the electrolyte, polymer-based solid-state electrolytes and functional additives can enhance the electrochemical stability window and thermodynamic safety. For example, self-healing polymers can alleviate mechanical stress accumulation during fast charging through dynamic hydrogen bonding or disulfide exchange mechanisms; gel electrolytes combine the high ionic conductivity of liquid electrolytes with the safety of solid-state electrolytes, with some gel electrolytes achieving room temperature ionic conductivities of up to 10⁻³ S/cm, approaching the level of liquid electrolytes.
Figure 3 Design Standards for Polymer Binders in High Energy Density Battery Cathodes
This figure outlines the four major design standards for polymer binders in high energy density battery cathodes. First, optimize the electrode-electrolyte interfacial compatibility by constructing an ordered interfacial passivation layer to suppress the dissolution of transition metal ions and electrolyte decomposition, such as PAA-PN binders that can reduce nickel deposition on lithium electrodes from 56.95 μg/L to 2.44 μg/L after cycling; second, suppress the structural stress evolution of the cathode through strong intermolecular interactions to buffer volume expansion (>8%), maintaining the continuity of the 3D conductive framework; third, construct a multi-scale charge transport network, where conjugated polymer binders reduce the activation energy for lithium ion diffusion through polar functional groups, enhancing charge transfer efficiency; fourth, enhance thermodynamic stability, where thermally stable polymer matrices (decomposition temperature > 300℃) can quench reactive oxygen species, raising the onset temperature for oxygen release by more than 50℃, thereby improving battery safety.
Figure 4 PAA-PN Binder’s Surface Protection Mechanism for NCM811
This figure illustrates the synthesis of PAA-PN crosslinked binders and their surface protection mechanism for the NCM811 cathode under high voltage, as well as the roles of other functional binders. Figure 4a shows a schematic of the formation of PAA-PN binders through the chemical crosslinking of PAA and PN; Figure 4b compares the structural changes of NCM811 under the influence of PVDF and PAA-PN binders, where PAA-PN forms a dense outer layer CEI and an inner layer defect passivation rock salt phase, suppressing transition metal dissolution and electrolyte oxidation; Figure 4c shows through ICP-MS analysis that after 200 cycles, the PAA-PN binder results in nickel deposition on lithium foil of only 2.44 μg/L, far lower than 56.95 μg/L for PVDF; Figures 4d-e illustrate the mechanism of natural wood-derived CEF binders in suppressing interfacial side reactions through electrostatic repulsion, reducing transition metal deposition in high-load OLO cathodes by >85%; Figure 4f shows the role of anti-aging binders in layered transition metal oxides, which can eliminate reactive oxygen species, stabilize the CEI layer, and enhance high-temperature and high-voltage performance.
Figure 5 c-IPN and PVBST Binders’ Performance
This figure illustrates the role of c-IPN and PVBST binders in enhancing battery performance. Figure 5a shows the advantages of c-IPN cathodes, which optimize the dispersion of active materials through electrostatic double layers; Figure 5b shows that c-IPN binders enhance the lithium ion diffusion coefficient (DLi⁺) across the entire voltage range, surpassing n-IPN; Figure 5c shows that soft-pack batteries composed of c-IPN cathodes and lithium metal anodes achieve energy densities of 376 Wh/kg and 1043 Wh/L at 45℃, with a capacity retention rate of 82% after 100 cycles; Figure 5d illustrates the design of PVBST binders, which achieve ultra-high damping, self-healing, and accelerated lithium ion transport, maintaining excellent cycling stability under high load in lithium-sulfur batteries, such as a sulfur loading of 4.72 mg/cm² with a capacity retention rate of 85% after 100 cycles.
Figure 6 Conductive Binders’ Structure and Performance
This figure illustrates the structures of various conductive binders and their enhancement of battery performance. Figure 6a shows the preparation process of PABS:PEDOT core-shell emulsion, where elastic copolymer cores trap polysulfides, and the PEDOT shell provides conductive pathways with a conductivity of > 10⁻² S/cm; Figure 6b shows that it enhances lithium-sulfur battery performance through elastic constraints, charge transfer enhancement, and accelerated polysulfide conversion; Figures 6c-d illustrate the PC-PTFE double binder system, which reduces the use of 70% PTFE, achieving a high load of 90 mg/cm², with a capacity retention rate of 84% after 50 cycles at 0.5C; Figure 6e shows the cycling performance of different binders at 25 mg/cm² load; Figure 6f illustrates the CPC binder stabilizing conjugated polymers with polyelectrolytes, achieving a discharge capacity of 65 mAh/g for LFP batteries at 6C (compared to only 2 mAh/g for PVDF), with a capacity retention rate of 63% after 400 cycles (compared to only 6% for PVDF).
Figure 7 Polymer Design for Enhanced Safety
This figure illustrates the design and performance of polymers that enhance battery safety. Figure 7a shows the self-assembled stable CEI layer formed by the amphiphilic copolymer electrolyte UMA-F on the surface of high-nickel cathodes, transforming oxygen release into Co³⁺→Co⁴⁺ oxidation, with stable cycling for 200 cycles at 4.7V and no short circuit at 120℃; Figure 7b shows the water-based binder PEI-TIC, which anchors polysulfides through a 3D crosslinked network and polar groups, achieving an initial capacity of 817.0 mAh/g for lithium-sulfur batteries at 0.2C, with a capacity retention rate of 97.2% after 800 cycles; Figures 7c-d illustrate the binder β-CDp-Cg-2AD, which limits polysulfides through ion-dipole interactions, achieving a capacity retention of 7.28 mAh/cm² after 100 cycles at a sulfur loading of 7.36 mg/cm², with an increased thermal decomposition temperature to delay thermal runaway.
Figure 8 Failure Mechanisms of Silicon-Based Anodes and Binder Design Principles
This figure illustrates the failure mechanisms of silicon-based anodes and the design principles of polymer binders. Silicon-based anodes experience volume expansion of up to 300%, leading to particle fracture, current collector delamination, and dynamic reconstruction of the SEI (failure mechanisms); binders need to address: constructing dynamic adaptive interfaces to cope with thermodynamic instability, buffering volume stress through molecular chain elasticity; forming robust chemical bond networks (such as hydrogen bonds, coordination bonds) to ensure adhesion of active materials to current collectors; optimizing electronic/ionic synergistic transport, enhancing charge transfer kinetics through conductive functional groups. For example, binders such as SA and CMC form hydrogen bonds with the silicon surface oxide layer through polar groups, but their linear structures struggle to withstand 300% expansion, necessitating crosslinking to form three-dimensional networks to enhance stability.
Figure 9 Performance Comparison of SA, CMC, PVDF, and Other Binders
This figure compares the mechanical properties and effects on batteries of sodium alginate (SA), carboxymethyl cellulose (CMC), PVDF, and other binders. Figures 9a-d show that in both dry and solvent-swollen states, the Young’s modulus of SA is 6.7 times that of PVDF, effectively suppressing the anisotropic expansion leading to fracture during the initial lithiation of silicon particles; Figure 9e shows the impact of different cellulose binders on irreversible loss during the first cycle; Figure 9f shows that the fracture strain of the 1C1E-Ca²⁺ binder reaches 4.0%, with a tensile strength of > 68 MPa, outperforming pure CMC; Figure 9g shows that the LiCMC-TA 3D crosslinked binder transforms the contact between silicon and binder interfaces from point-line to surface contact, suppressing crack propagation; Figure 9h shows that PAA exhibits superior adsorption isotherms on graphite surfaces compared to CMC; Figure 9i shows that low molecular weight PAA demonstrates better swelling behavior in diethyl carbonate vapor than NaCMC, aiding in maintaining electrode structure.
Figure 10 Self-Healing Binders and Their Effects on Silicon-Based Anodes
This figure illustrates the effects of self-healing binders and functional binders on the performance of silicon-based anodes. Figure 10a shows the PAA-DA/PVA double network binder, which buffers stress through dynamic hydrogen bonds and covalent crosslinking, achieving a capacity retention of 1974.1 mAh/g for Si@PAA-DA/PVA electrodes after 500 cycles at 4 A/g; Figure 10b shows a hyperbranched topological polymer self-healing binder that repairs micro-defects through hydrogen bond network reconstruction, maintaining electrical contact; Figure 10c illustrates a zwitterionic binder that regulates interfacial electrochemistry, inducing the formation of a thin and uniform SEI layer; Figure 10d shows a mussel-inspired PCH-CR binder, where soft-hard segments synergistically enhance mechanical strength and adhesion, improving the dynamic stability of the SEI.
Figure 11 Design of Polymer Interface Stabilizers for Lithium Metal Anodes
This figure outlines the design principles of polymer interface stabilizers for lithium metal anodes. Lithium metal anodes face challenges due to thermodynamic instability (reacting with electrolytes to form porous SEI), dynamic volume changes (>200%), and electrochemical polarization (dendrite growth under high currents); stabilizers need to: construct composite SEI layers with high ionic conductivity and Young’s modulus; establish uniform lithium ion transport channels to eliminate current density gradients; be compatible with existing battery systems without reducing energy density. For example, in situ polymerized acrylate polymer layers form gradient modulus structures, suppressing dendrite penetration and buffering volume strain, with some designs enabling symmetrical batteries to cycle for over 1000 hours.
Figure 12 Ideal vs. Actual Lithium Metal Deposition
This figure compares the actual deposition characteristics of lithium metal during battery charging with the ideal plating morphology. In actual deposition, lithium metal tends to form dendrites due to interfacial electrocrystallization kinetics, with curvature-driven growth mechanisms leading to irregular shapes, posing risks of internal short circuits and capacity decay; ideally, lithium ions deposit uniformly to form a dense, flat metal layer. Controlling lithium deposition kinetics (such as nucleation sites, growth orientation, ion concentration gradients) is key to achieving ideal deposition, for example, COF-based artificial SEI layers guide uniform nucleation through ion sieving effects of sub-nanopores, with a Young’s modulus of 6.8 GPa suppressing dendrite growth, enabling symmetrical batteries to cycle for over 400 hours at 1 mA/cm².
Figure 13 Performance of Artificial SEI Layers like COF-Li
This figure illustrates the stabilizing effects of artificial SEI layers such as COF-Li and P (St-MaI) on lithium metal anodes. Figure 13a shows the in situ polymerization of COF on the lithium surface; Figures 13b-c show that the sub-nanopores of COF regulate lithium ion flux, guiding uniform nucleation; Figure 13d shows that the Young’s modulus of COF-SEI is 6.8 GPa, exceeding the yield strength of lithium dendrites; Figure 13e shows that COF-Li enables symmetrical batteries to cycle for over 400 hours at 1 mA/cm² and 1 mAh/cm²; Figure 13f shows that P (St-MaI) regulates lithium ion solvation and transport through carboxyl and crown ether units, guiding uniform deposition; Figures 13g shows that P (St-MaI)@Li enables symmetrical batteries to cycle for over 900 hours at 1 mA/cm², with Li||LiFePO₄ batteries maintaining a capacity retention of 96% after 930 cycles at 1C.
Figure 14 Cycling Stability of Different Polymer Interface Layers
This figure illustrates the cycling stability of lithium metal electrodes modified with different polymer interface layers. Figure 14a shows the cross-section SEM of LiPEO-UPy@Li anodes, where a 70 nm coating suppresses dendrite growth under high surface capacity (10 mAh/cm²); Figure 14b shows that its symmetrical battery cycles for over 1000 hours at 5 mA/cm²; Figure 14c shows that the PMF/Cu electrode maintains a coulombic efficiency of 94.7% after 50 cycles at 10 mA/cm²; Figure 14d shows that Li (PECA+LiNO₃) maintains a capacity retention of 93% after 500 cycles in LiFePO₄||Li batteries at 2C; Figure 14e shows that LPEDV-Li symmetrical batteries cycle for over 1200 hours at 5 mA/cm² and 5 mAh/cm²; Figure 14f shows that lithium electrodes modified with PDDA-TFSI layers cycle for over 700 hours at 1 mA/cm² and 10 mAh/cm², regulating deposition orientation through electrostatic shielding.
Figure 15 Design of Gel Electrolytes
This figure illustrates the design of gel electrolytes modified with different chain segments and functional groups. Figure 15a shows that F-GPE forms a dynamic adaptive interface layer through in situ copolymerization of MMA, TEGDMA, and ETPTA, achieving an ionic conductivity of 2.24×10⁻⁴ S/cm; Figure 15b shows that PEGDME@PMMA composite electrolytes achieve ionic conductivities of 1.1×10⁻⁴ S/cm at 30℃ and 1.0×10⁻³ S/cm at 80℃, with an electrochemical window of 4.7 V; Figure 15c shows that BPE enhances the cycling stability of 4.5 V LiCoO₂||Li batteries, outperforming PEO-based electrolytes after 80 cycles; Figure 15d shows that CDPE constructs a crosslinked network through hydrogen bonding with carbon dots and PDOL, achieving an ionic conductivity of 3.20 mS/cm; Figures 15e-f show that GPEs containing amide functional groups enhance mechanical properties and improve dendrite suppression capabilities through chemical crosslinking and hydrogen bonding.
Figure 16 Composite and Formulation Optimized Gel Electrolytes
This figure illustrates the design of composite-filled and formulation-optimized gel electrolytes. Figure 16a shows that SIC composite electrolytes exhibit superior thermal stability compared to commercial PP separators, enhancing the cycling stability of NCM523 and LiFePO₄ batteries; Figure 16b shows that PVEC-APTES-LLZTO composite electrolytes enhance interfacial compatibility through chemical bonding, improving the energy density of lithium cobalt oxide-based solid-state batteries; Figure 16c shows that LSC nanofiber framework composite electrolytes achieve an ionic conductivity of 1.50 mS/cm at 25℃ and a lithium ion transference number of 0.91; Figure 16d shows that GPEs containing ionic liquid end groups optimize lithium ion transport, achieving a room temperature conductivity of 2.6 mS/cm; Figures 16e-f show that Pyr13FSI hybrid network GPEs achieve a room temperature conductivity of > 1 mS/cm; Figures 16g-h show that MB-GPE regulates solvation structures through fluorinated solvents, cycling lithium electrodes for over 3200 hours at 0.5 mA/cm²; Figure 16i shows that deep eutectic gel electrolytes achieve a conductivity of 1.67 mS/cm at 30℃, with LiCoO₂||Li batteries maintaining a capacity retention of 72.5% after 1500 cycles at 4.45 V.
Figure 17 Design of MOF-Based Electrolytes
This figure illustrates the design and performance of MOF-based electrolytes. Figure 17a shows that SPE2-PI-ZIF8 electrolytes stabilize lithium symmetrical batteries at room temperature, with a lithium ion transference number of 0.68; Figure 17b shows that PEO/LiTFSI-ILE-ZIF-67 electrolytes achieve a conductivity of 1.19×10⁻⁴ S/cm at 25℃ and an electrochemical window of 5.66 V; Figure 17c shows that CIL-MOF/PVDF solid-state electrolytes achieve a capacity retention of 98.9% after 500 cycles at 6C under a 4.82 V window; Figure 17d shows that UIO-66-NH₂ enhances lithium salt dissociation, improving electrolyte performance; Figure 17e shows that Zr-BPDC-SO₃H MOF forms a 3D network on nanocellulose, achieving a conductivity of 7.88×10⁻⁴ S/cm and a transference number of 0.88; Figures 17f shows that H-ZIF-8/HNT electrolytes achieve a conductivity of 7.74×10⁻³ S/cm and a transference number of 0.84.
Figure 18 Design of COF/HOF-Based Electrolytes
This figure illustrates the design and performance of COF and HOF-based electrolytes. Figure 18a shows that NCS-Li COF electrolytes achieve a room temperature conductivity of 1.49 mS/cm and a transference number of 0.84 without solvents; Figure 18b shows that COF-531, linked by urea bonds, forms nitrogen-rich coordination sites through a dynamic reversible network, promoting lithium ion transport; Figure 18c shows that zwitterionic COF electrolytes achieve a room temperature conductivity of 1.65×10⁻⁴ S/cm, with solid-state batteries maintaining a capacity retention of 99% after 100 cycles; Figure 18d shows that gel electrolytes modified with TpPa-2 COF induce the formation of LiF-rich SEI, with LiFePO₄||Li batteries maintaining a capacity retention of 75% after 1000 cycles at 0.5C; Figure 18e shows that PVDF-TpPaSO₃Li electrolytes enable symmetrical batteries to cycle for over 2500 hours at 60℃; Figure 18f shows that HT-HOF-IL CQSE achieves a conductivity of 5.8×10⁻⁴ S/cm at -20℃ and 5.7×10⁻⁵ S/cm at 60℃, with a transference number of 0.69.
Conclusion and Outlook
Polymer materials, with their designable structures, mechanical flexibility, and multifunctional adaptability, have become key materials driving advancements in high energy density lithium-ion battery technology. As core components of electrolytes, binders, and composite electrodes, polymers exhibit excellent performance in high energy density and high safety battery systems: in electrolyte engineering, solid-state/gel polymer electrolytes significantly enhance safety by suppressing lithium dendrite growth and improving interfacial compatibility; in electrode materials, conductive polymers and functional binders address cycling stability issues of high-capacity silicon-based anodes and sulfur cathodes by alleviating volume expansion and parasitic reactions; moreover, polymer-based composites provide innovative pathways to break through the energy density limitations of traditional electrode materials.
Despite their immense potential, the application of polymers still faces challenges in structural stability, ionic transport efficiency, processing technologies, and system integration, such as oxidative degradation of high-voltage cathode binders, insufficient dynamic self-healing capabilities of silicon-based anode binders, and limitations in room temperature ionic conductivity of polymer electrolytes. Additionally, controlling coating uniformity, cost-effectiveness, and environmental sustainability requirements in large-scale production necessitate collaborative innovations in materials science and manufacturing engineering.
Future research should focus on: innovative polymer structural designs that balance high chemical/mechanical stability with rapid ionic transport; optimizing interfaces and achieving multi-scale synergy to enhance compatibility and suppress side reactions through multifunctional interfacial layers; developing advanced processing and system integration technologies, such as 3D printing and electrospinning for the large-scale production of uniform films or flexible electrodes; promoting interdisciplinary innovations that integrate computational materials science, in situ characterization, and sustainable chemistry to accelerate polymer design; reducing industrial production costs by minimizing material usage and introducing smart manufacturing equipment; and improving recycling systems to develop multi-process routes for achieving high recovery rates in safe recycling.
Polymer-based high energy density lithium-ion batteries are expected to achieve breakthroughs in energy density (>500 Wh/kg), inherent safety (through solid-state structures), and cycle life (>2000 cycles), but commercialization requires collaborative solutions from academia, industry, and research to address the “last mile” challenges from the laboratory to the market. Furthermore, polymer materials also hold transformative potential in next-generation energy storage systems such as sodium-ion batteries and lithium-sulfur batteries through innovative interfacial engineering and multifunctional composite solutions.
Advancements in polymer materials for high-energy-density lithium-ion batteries
Chem. Soc. Rev., 2025, Advance Article
https://doi.org/10.1039/D5CS00583C