From blocker to booster: Harnessing garnet surface chemistry for advanced solid-state electrolytes

Solid‐state lithium batteries (SSLBs) with composite solid electrolytes (CSEs) offer enhanced energy density and high safety. However, their performance is hindered by large thickness and limited Li⁺ conductivity of CSEs, and large electrode/electrolyte interface resistance. This study develops an 18 µm‐thick CSE using a polyethylene scaffold, which incorporates garnet‐type Li6.25La3Zr2Ga0.25O12 (LLZGO) oxide and an ionic liquid (IL) additive in a poly(vinylidene fluoride‐co‐hexafluoropropylene)/polypropylene carbonate matrix, achieving a high ionic conductivity of 8.6 × 10−4 S cm−1 at 30 °C. The IL increases Li+ conduction of the CSE and reduces the interfacial resistance. The constructed LiNi0.8Co0.1Mn0.1O2 (NCM‐811)||CSE||Li cell shows remarkable charge–discharge performance. This study also integrates LLZGO and N‐propyl‐N‐methylpyrrolidinium bis(trifluorosulfonyl)imide (PMP‐TFSI) IL into a thick NCM‐811 cathode. The synergy between LLZGO and PMP‐TFSI within the cathode is examined. A high‐mass‐loading cathode with ≈20 mg cm−2 NCM‐811 is developed. The resulting composite cathode||CSE||Li cell achieves an areal capacity of ≈4 mAh cm−2. With the proposed scaffold‐supported CSE and thick NCM/LLZGO/IL composite cathode, the projected energy density of the resulting anode‐free pouch cell is ≈420 Wh kg−1. This study demonstrates a scalable and effective strategy for fabricating an oxide‐based SSLB with a high energy density and enhanced Li+ transport properties.

Sodium-ion batteries (SIBs) are emerging as a promising alternative to lithium-ion batteries, primarily due to their plentiful raw materials and cost-effectiveness. However, the use of traditional organic liquid electrolytes in sodium battery applications presents significant safety risks, prompting the investigation of solid electrolytes as a more viable solution. Despite their advantages, single solid electrolytes encounter challenges, including low conductivity of sodium ions at room temperature and incompatibility with electrode materials. To overcome these limitations, the researchers develop composite polymer solid electrolytes (CPSEs), which merge the strengths of high ionic conductivity of inorganic solid electrolytes and the flexibility of polymer solid electrolytes. CPSEs are usually composed of inorganic materials dispersed in the polymer matrix. The final performance of CPSEs can be further improved by optimizing the particle size, relative content, and form of inorganic fillers. CPSEs show great advantages in improving ionic conductivity and interface compatibility, making them an important direction for future solid-state sodium battery research. Therefore, this paper summarizes recent advancements in composite solid electrolytes, discusses the impact of their preparation processes on performance, and outlines potential future developments in sodium-ion solid-state batteries.

Synergistic design of 3D Na3.2Zr1.9Ca0.1Si2PO12-based composite solid electrolyte via in-situ polymerization for solid-state sodium batteries.

Composite solid electrolyte with improved ionic conductivity and high lithium transference number through reduced PVDF-HFP crystallinity

Garnet‐type oxide Li6.4La3Zr1.4Ta0.6O12 (LLZTO) features superior ionic conductivity and good stability toward lithium (Li) metal, but requires high‐temperature sintering (≈1200 °C) that induces high fabrication cost, poor mechanical processability, and high interface resistance. Here, a novel high‐performance tricomponent composite solid electrolyte (CSE) comprising LLZTO−4LiBH4/xLi3BN2H8 is reported, which is prepared by ball milling the LLZTO−4LiBH4 mixture followed by hand milling with Li3BN2H8. Green pellets fabricated by heating the cold‐pressed CSE powders at 120 °C offer ultrafast room‐temperature ionic conductivity (≈1.73 × 10−3 S cm−1 at 30 °C) and ultrahigh Li‐ion transference number (≈0.9999), which enable the Li|Li symmetrical cells to cycle over 1600 h at 30 °C with only 30 mV of overpotential. Moreover, the Li|CSE|TiS2 full cells deliver 201 mAh g−1 of capacity with long cyclability. These outstanding performances are due to the low open porosity in the electrolyte pellets as well as the high intrinsic ionic conductivity and easy deformability of Li3BN2H8.

An all-solid-state lithium battery using the Li7La3Zr2O12 and Li6.7La3Zr1.7Ta0.3O12 ceramic enhanced polyethylene oxide electrolytes with superior electrochemical performance

Flexible poly(ethylene carbonate)/garnet composite solid electrolyte reinforced by poly(vinylidene fluoride-hexafluoropropylene) for lithium metal batteries

Synthesis and characterization of LAGP-glass-ceramics-based composite solid polymer electrolyte for solid-state Li-ion battery application

Cellulosic all-solid-state electrolyte for lithium batteries fabricated via bio-synthetic avenue

Preparation, characterization and ionic conductivity studies of composite sulfide solid electrolyte

Solid polymer electrolytes (SPEs) are regarded as promising candidates for next-generation solid-state lithium metal batteries (SSLMBs) due to their high flexibility and excellent processability, whereas their practical application remains a challenge to simultaneously achieve high ionic conductivity, superior inherent stability, and desirable interfacial compatibility with the Li metal anode. Here, we report a composite solid electrolyte (CSE) incorporating a three-dimensional zeolite network (3D Zeo) into a poly(ethylene oxide) (PEO) matrix containing lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt (3D Zeo/PEO). The interconnected 3D Zeo provides continuous Li+-conduction pathways and promotes the amorphization of the polymer and the dissociation of the Li salt via Lewis acid–base interactions. The resulting 3D Zeo/PEO CSE exhibits an ionic conductivity of 1.62 × 10−4 S cm−1 at room temperature and an electrochemical stability window up to 5.7 V vs. Li+/Li, significantly surpassing those of LiTFSI–PEO SPE (3.23 × 10−6 S cm−1, 4.9 V). Leveraging the regulatory effect of the 3D Zeo/PEO CSE on Li+ deposition and solid electrolyte interphase formation, the symmetric cell demonstrates stable cycling over 2300 h with an overpotential of 0.13 V, and the full cells also deliver superior high-rate capability and long-term stability with a capacity retention of 92% after 500 cycles at room temperature, far exceeding the performance of batteries using LiTFSI–PEO SPE and CSE with zeolite-based particle fillers. This work provides a promising approach for the design of CSEs to achieve high interfacial compatibility and uniform Li+ deposition for next-generation SSLMBs.

A general strategy for all-solid-state batteries with agglomeration-free and high conductivity achieved by improving the interface compatibility of fillers and polymer matrix

Chemically bonding inorganic fillers with polymer to achieve ultra-stable solid-state sodium batteries

A composite solid electrolyte with a framework of vertically aligned perovskite for all-solid-state Li-metal batteries

Garnet‐type solid‐state electrolytes (SSEs) are a remarkable Li‐ion electrolyte for the realization of next‐generation all‐solid‐state lithium batteries due to their excellent stability against Li metal as well as high ionic conductivities at room temperature. However, garnet electrolytes always contain undesired and hardly removable Li2CO3 contaminations that have persistently large resistance and unstable interface contact with Li metal. This is a critical bottleneck for the practical application of garnet electrolytes. Here, we design a novel strategy to completely root out Li2CO3 both inside and on the surface of garnet. This is achieved by a so‐called double replacement reaction between Li2CO3 and SiO2 during one‐step hot press process for garnet electrolyte densification. It leads to in‐situ transformation of LixSiOy (LSO) mostly locating around the grain boundaries of garnet. Due to the higher ion conductivity and better electrochemistry stability of LSO than Li2CO3, the modified garnet electrolyte shows much improved electrochemical performance. Moreover, the wettability between modified garnet electrolyte and lithium metals was significantly enhanced in the absence of surface Li2CO3. As a proof of concept, an assembled Li symmetric cell with modified garnet electrolyte displays a high critical current density (CCD) of 0.7 mA cm−2 and a low interfacial impedance (5 Ω cm2) at 25 °C. These results indicate that the upcycling of Li2CO3 is a promising strategy to well‐address the degradation and interfacial issue associated with garnet electrolytes.