Conversion-type cathodes with multiple-electron transfer capability are a promising platform for high-energy lithium-ion batteries. However, their full potential is often unrealized due to sluggish kinetics at the nanoscale, where complex phase transformations disrupt charge transport and ultimately limit performance. To address this fundamental challenge, we reconcile the contrasting electrochemical reversibility of the isostructural FeF2 and CuF2 cathode, the latter of which has historically been limited by irreversibility. By infiltrating liquid gallium (Ga) into a CuF2/carbon matrix, a percolation network (pGa-CuF2/C) is established, enabling reversible two-electron transfer nanoscale conversion via a displacement-reaction pathway, similar to that of FeF2. Our mechanistic studies reveal that the Ga interlayer retards fluorine mobility, fostering the Li2CuF4 intermediate phase. Crucially, Ga synergistically minimizes the lattice mismatch and interfacial energy at Li2CuF4|Cu interfaces, ensuring homogeneous nucleation and the formation of a bicontinuous copper network interconnected with LiF. An optimized pGa-CuF2/C@TiO2 core-shell structure achieves a notable capacity of ∼300 mAh/g at an average voltage of 2.8 V after 20 cycles. These mechanistic insights demonstrate that interfacial kinetics dictate the pathway of conversion reactions, highlighting the importance of modulating interfacial energy and lattice mismatch to unlock the broader potential of conversion cathodes.

Correction for ‘A relaxor ferroelectric polymer with an ultrahigh dielectric constant largely promotes the dissociation of lithium salts to achieve high ionic conductivity’ by Yan-Fei Huang et al. , Energy Environ. Sci. , 2021, 14 , 6021–6029, https://doi.org/10.1039/D1EE02663A.

The composite solid-state electrolytes (CSEs) are one of the most promising electrolytes for advanced solid-state Li metal batteries. However, it is unclear for the effect of the induced electric field inside CSEs on the Li-ion transport. Herein, we design a compact CSE by imbedding the lithium niobate (LiNbO3) with both high ionic conductivity and dielectric constant into poly(vinylidene fluoride) matrix (NPC). The LiNbO3 significantly enhances the internal electric field of NPC along the LiNbO3 particles and establishes uniform interfacial electric field between NPC and electrodes, which fundamentally facilitates the Li-ion transport, weakens the space-charge layer and inhibits the growth of Li dendrites. Continuous fast ion-conducting channels with high concentration of Li-ions are constructed inside NPC, which contributes to a quite high ionic conductivity (7.39×10−4 S cm−1, 25°C) and ultra-low activation energy (0.112 eV). The LiNi0.8Co0.1Mn0.1O2/NPC/Li solid-state batteries exhibit quite stable cycling performance at 25°C.

The application of poly(ethylene oxide) (PEO)-based polymer electrolytes has been impeded due to extremely low room-temperature ionic conductivity and inevitable Li penetration. Herein, FeF3.3H2O is demonstrated to be a valid additive in PEO to improve the Li+ transfer dynamics as well as manipulate profitable interface chemistry on Li metal surface at the molecular level. Combining experimental and theoretical investigations, we find that the Fe3+ ions could accelerate the mobility of Li+ ions due to the strong coordination with ether oxygen and anions. More impressively, the inorganic-organic bilayer heterogeneous SEI interphase triggered by the strong coordination effect of Fe3+ ensures dendrite-free anode during long cycling. Consequently, the Fe3+-integrated PEO electrolytes deliver a remarkable critical current density of 1.3 mA cm-2. Coupled with its high anodic stability, the competitive all-solid-state Li||Li and Li||LiFePO4 cells endow unprecedented lifespan over up to 1000 cycles at 0.2 mA cm-2 and 800 cycles at 0.5 C, respectively. Intriguingly, tailoring heterogeneous interfacial chemistry by FeF3.3H2O is further demonstrated with the LiFePO4-based pouch cells, providing the pioneering levels for practical all-solid-state batteries.

The application of poly(ethylene oxide) (PEO)-based polymer electrolytes has been impeded due to extremely low room-temperature ionic conductivity and inevitable Li penetration. Herein, FeF3.3H2O is demonstrated to be a valid additive in PEO to improve the Li+ transfer dynamics as well as manipulate profitable interface chemistry on Li metal surface at the molecular level. Combining experimental and theoretical investigations, we find that the Fe3+ ions could accelerate the mobility of Li+ ions due to the strong coordination with ether oxygen and anions. More impressively, the inorganic-organic bilayer heterogeneous SEI interphase triggered by the strong coordination effect of Fe3+ ensures dendrite-free anode during long cycling. Consequently, the Fe3+-integrated PEO electrolytes deliver a remarkable critical current density of 1.3 mA cm-2. Coupled with its high anodic stability, the competitive all-solid-state Li||Li and Li||LiFePO4 cells endow unprecedented lifespan over up to 1000 cycles at 0.2 mA cm-2 and 800 cycles at 0.5 C, respectively. Intriguingly, tailoring heterogeneous interfacial chemistry by FeF3.3H2O is further demonstrated with the LiFePO4-based pouch cells, providing the pioneering levels for practical all-solid-state batteries.

Ni‐rich layered oxides as the cathode materials of high‐energy‐density lithium‐ion batteries (LIBs) suffer from capacity decay and structural instability owing to oxygen loss during cycling. It is a huge challenge to prevent the oxygen loss of Ni‐rich cathode materials during long cycling. Here, a pre‐deoxidation of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) single crystal materials is achieved by heat treatment at elevated temperatures in argon condition to form a stable surface with rock salt structure. The stable surface structure with oxygen vacancy defects successfully suppresses the harmful phase transitions of NCM811 and effectively improves the stability of the NCM811/electrolyte interface during cycling at a high cut‐off voltage. In addition, the intragranular structural evolution and cation mixing degree is inhibited to effectively suppress the intergranular cracking and particle pulverization of cathode during long cycling. The pre‐deoxidation of NCM811 exhibits 70.6% capacity retention after 1000 cycles at the current density of 0.5 C between 2.8 and 4.3 V, which is much larger than that of pristine NCM811 capacity retention of 27.3%. The strategy of pre‐deoxidation of Ni‐rich layered structure cathode to regulate the defect chemistry and surface structure provides a facile and effective way to achieve long cycling life high‐energy density LIBs.

The fillers in composite solid-state electrolyte are mainly responsible for the enhancement of the conduction of Li ions but barely regulate the formation of solid electrolyte interphase (SEI). Herein, a unique filler of dielectric NaNbO3 for the poly(vinylidene fluoride) (PVDF)-based polymer electrolyte, which is subjected to the exchange of Li+ and Na+ during cycling, is reported and the substituted Na+ is engaged in the construction of a fluorinated Li/Na hybrid SEI with high Young's modulus, facilitating the fast transport of Li+ at the interface at a high areal capacity and suppressing the Li dendrite growth. The dielectric NaNbO3 also induces the generation of high-dielectric β phase of PVDF to promote the dissociation of Li salt. The Li/Li symmetrical cell exhibits a long-term dendrite-free cycling over 600 h at a high areal capacity of 3 mA h cm-2. The LiNi0.8Mn0.1Co0.1O2/Li solid-state cells with NaNbO3 stably cycle 2200 times at 2 C and that paired with high-loading cathode (10 mg cm-2) can stably cycle for 150 times and exhibit excellent performances at -20 °C. This work provides a novel design principle of fillers undertaking interfacial engineering in composite solid-state electrolytes for developing the safe and stable solid-state lithium metal battery.

The authors developed a highly conductive and dielectric composite solid-state electrolyte by coupling BaTiO3 and Li0.33La0.56TiO3-x nanowires with a side-by-side heterojunction structure in a polyvinylidene difluoride matrix, which simultaneously promotes the dissociation of lithium salts to produce more movable Li ions and efficiently transports the generated movable Li ions. The ionic conductivity of composite solid-state electrolytes does not meet the application requirements of solid-state lithium (Li) metal batteries owing to the harsh space charge layer of different phases and low concentration of movable Li+. Herein, we propose a robust strategy for creating high-throughput Li+ transport pathways by coupling the ceramic dielectric and electrolyte to overcome the low ionic conductivity challenge of composite solid-state electrolytes. A highly conductive and dielectric composite solid-state electrolyte is constructed by compositing the poly(vinylidene difluoride) matrix and the BaTiO3-Li0.33La0.56TiO3-x nanowires with a side-by-side heterojunction structure (PVBL). The polarized dielectric BaTiO3 greatly promotes the dissociation of Li salt to produce more movable Li+, which locally and spontaneously transfers across the interface to coupled Li0.33La0.56TiO3-x for highly efficient transport. The BaTiO3-Li0.33La0.56TiO3-x effectively restrains the formation of the space charge layer with poly(vinylidene difluoride). These coupling effects contribute to a quite high ionic conductivity (8.2 x 10(-4) S cm(-1)) and lithium transference number (0.57) of the PVBL at 25 degrees C. The PVBL also homogenizes the interfacial electric field with electrodes. The LiNi0.8Co0.1Mn0.1O2/PVBL/Li solid-state batteries stably cycle 1,500 times at a current density of 180 mA g(-)(1), and pouch batteries also exhibit an excellent electrochemical and safety performance.

The application of poly(ethylene oxide) (PEO)-based polymer electrolytes has been impeded due to extremely low room-temperature ionic conductivity and inevitable Li penetration. Herein, FeF3.3H2O is demonstrated to be a valid additive in PEO to improve the Li+ transfer dynamics as well as manipulate profitable interface chemistry on Li metal surface at the molecular level. Combining experimental and theoretical investigations, we find that the Fe3+ ions could accelerate the mobility of Li+ ions due to the strong coordination with ether oxygen and anions. More impressively, the inorganic-organic bilayer heterogeneous SEI interphase triggered by the strong coordination effect of Fe3+ ensures dendrite-free anode during long cycling. Consequently, the Fe3+-integrated PEO electrolytes deliver a remarkable critical current density of 1.3 mA cm-2. Coupled with its high anodic stability, the competitive all-solid-state Li||Li and Li||LiFePO4 cells endow unprecedented lifespan over up to 1000 cycles at 0.2 mA cm-2 and 800 cycles at 0.5 C, respectively. Intriguingly, tailoring heterogeneous interfacial chemistry by FeF3.3H2O is further demonstrated with the LiFePO4-based pouch cells, providing the pioneering levels for practical all-solid-state batteries.

The ionic conductivity of composite solid-state electrolytes does not meet the application requirements of solid-state lithium (Li) metal batteries owing to the harsh space charge layer of different phases and low concentration of movable Li + . Herein, we propose a robust strategy for creating high-throughput Li + transport pathways by coupling the ceramic dielectric and electrolyte to overcome the low ionic conductivity challenge of composite solid-state electrolytes. A highly conductive and dielectric composite solid-state electrolyte is constructed by compositing the poly(vinylidene difluoride) matrix and the BaTiO 3 –Li 0.33 La 0.56 TiO 3– x nanowires with a side-by-side heterojunction structure (PVBL). The polarized dielectric BaTiO 3 greatly promotes the dissociation of Li salt to produce more movable Li + , which locally and spontaneously transfers across the interface to coupled Li 0.33 La 0.56 TiO 3– x for highly efficient transport. The BaTiO 3 –Li 0.33 La 0.56 TiO 3– x effectively restrains the formation of the space charge layer with poly(vinylidene difluoride). These coupling effects contribute to a quite high ionic conductivity (8.2 × 10 −4 S cm −1 ) and lithium transference number (0.57) of the PVBL at 25 °C. The PVBL also homogenizes the interfacial electric field with electrodes. The LiNi 0.8 Co 0.1 Mn 0.1 O 2 /PVBL/Li solid-state batteries stably cycle 1,500 times at a current density of 180 mA g − 1 , and pouch batteries also exhibit an excellent electrochemical and safety performance.

A unique relaxor ferroelectric P(VDF-TrFE-CTFE) is investigated as a matrix of SPEs. The P(VDF-TrFE-CTFE) with ultrahigh ε r promotes the dissociation of LiTFSI to greatly enhance the ionic conductivity and the transference number of lithium ions.

The extremely low room-temperature ionic conductivity of solid-state polymer electrolytes (SPEs) ranging from 10(-7) to 10(-5) S cm(-1) seriously restricts their practical application in solid-state lithium metal batteries (LMBs). Herein, a unique relaxor ferroelectric (RFE) polymer of poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] is first investigated as a matrix of SPEs. We find that the P(VDF-TrFE-CTFE) with an ultrahigh dielectric constant (epsilon(r)) of 44 presents a stronger solvation ability towards lithium ions, which promotes the dissociation of LiN(SO2CF3)(2) to form more free charge carriers and enhances their mobility compared to the conventional PVDF with a low epsilon(r) of 9. The P(VDF-TrFE-CTFE) based SPEs show a much higher ionic conductivity of 3.10 x 10(-4) S cm(-1) at 25 degrees C and lower activation energy (0.26 eV) than PVDF based SPEs (1.77 x 10(-5) S cm(-1) and 0.49 eV). The PVDF blended with the P(VDF-TrFE-CTFE) or dielectric fillers such as BaTiO3 further confirm that the hybrid electrolytes with a larger epsilon(r) show a higher ionic conductivity. In addition, very tight interfaces of P(VDF-TrFE-CTFE) based SPEs with both the cathode and Li metal anode are constructed to ensure a stable interfacial resistance during cycling. The LiFePO4/Li and LiNi0.8Co0.1Mo0.1O2/Li batteries using P(VDF-TrFE-CTFE) based SPEs present a stable cycling performance at 25 degrees C. This work proposes a new strategy and opens a new research area to construct SPEs with high ionic conductivity by greatly increasing the epsilon(r) of polymers.