Composite Electrolyte for All‐Solid‐State Lithium Batteries: Low‐Temperature Fabrication and Conductivity Enhancement

Abstract

All-solid-state lithium batteries offer notable advantages over conventional Li-ion batteries with liquid electrolytes in terms of energy density, stability, and safety. To realize this technology, it is critical to develop highly reliable solid-state inorganic electrolytes with high ionic conductivities and adequate processability. Li Al Ti (PO ) (LATP) with a NASICON (Na superionic conductor)-like structure is regarded as a potential solid electrolyte, owing to its high "bulk" conductivity (ca. 10 S cm ) and excellent stability against air and moisture. However, the solid LATP electrolyte still suffers from a low "total" conductivity, mainly owing to the blocking effect of grain boundaries to Li conduction. In this study, an LATP-Bi O composite solid electrolyte shows very high total conductivity (9.4×10 S cm ) at room temperature. Bi O acts as a microstructural modifier to effectively reduce the fabrication temperature of the electrolyte and to enhance its ionic conductivity. Bi O promotes the densification of the LATP electrolyte, thereby improving its structural integrity, and at the same time, it facilitates Li conduction, leading to reduced grain-boundary resistance. The feasibility of the LATP-Bi O composite electrolyte in all-solid-state Li batteries is also examined in this study.

Solid‐State Lithium Batteries: Bipolar Design, Fabrication, and Electrochemistry

“…[102] In particular, Li 1 + x Al x M 2-x (PO 4 ) 3 (M=Ti or Ge) exhibits high bulk conductivity (~1.0 × 10 À 3 S cm À 1 ) at 25°C with excellent stability against moisture. [15,103] Technical approaches aimed at maximizing the total Li + conductivity of these materials may be divided into two categories; [104][105][106][107] (i) chemical substitution with trivalent or pentavalent ions (e. g., Al 3 + or Nb 5 + ) for Ti 4 + to change the bottleneck sizes for Li + transport; [15] and (ii) incorporation of secondary phases (e. g., Bi 2 O 3 ) in the fabrication step of SE sheets to tune the microstructure and thus to enhance boundary conductivity. [15,[108][109][110][111][112] Both [113] Interestingly, the LiPON-protected LATP exhibited an expanded electrochemical window of 0-5.0 V vs Li/Li + without undesirable side reactions with Li.…”

Multilayered, Bipolar, All‐Solid‐State Battery Enabled by a Perovskite‐Based Biphasic Solid Electrolyte

“…[32] The area of the cathode used in the cointype unit cell was 0.785 cm À2 ,a nd the cathode mass loading was about 2.2 mg cm À2 .I nt he case of the pouch-type bipolar batteries, ac ladded substrate (thickness % 20 mm) with Al and Cu layers was used as the bipolar plate. The cointype unit cell consisted of am etallic Li anode (negative electrode), BSE (or PSE), and ac omposite cathode (positive electrode).…”

“…[5][6][7][8][9][10][11][12][13] However,t here are practical challenges that hindert heir successful application in large-scale bipolar ASSBs. [26][27][28][29][30][31][32] Despite all of these merits,h owever,t hey require ah igh-temperatures intering process to achieve acceptable ionic conductivity.T he high-temperature process not only causesd eleterious reactions between the electrolytes and electrodes and damage to other components, but also makes it difficult to fabricate thin and large-area electrolyte sheets for ASSBs. [21][22][23][24][25] Therefore, utmost caution mustb ee xercised when synthesizing/handling materials and fabricating batteries.…”

“…Although sulfide-baseds olid electrolytes, such as Li 7 P 3 S 11 (LPS), Li 10 GeP 2 S 12 (LGPS),g lass ceramics, and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 ,p ossessh igh ionic conductivities at room temperature (2.5 10 À2 to 1.0 10 À3 Scm À1 ), they suffer from chemical/structural instability against moisture. [28][29][30][31][32] Furthermore, hard and brittle features of the sintered electrolyte sheets inhibitc lose contact betweent he electrolyte and electrode;t hus leading to both poor electrochemical performance and reliability of ASSBs. Oxide-based solid electrolytes, fore xample, perovskite-, NASICON-, and LISI-CON-based compounds, offer many advantages, such as good chemical/structural stabilityi nahumid atmosphere and aw ide operating temperature range, over sulfides (although garnettype oxides are known to have chemical instability against moisture, resulting in the formation of LiOH and Li 2 CO 3 ).…”

“…Oxide-based solid electrolytes, fore xample, perovskite-, NASICON-, and LISI-CON-based compounds, offer many advantages, such as good chemical/structural stabilityi nahumid atmosphere and aw ide operating temperature range, over sulfides (although garnettype oxides are known to have chemical instability against moisture, resulting in the formation of LiOH and Li 2 CO 3 ). [26][27][28][29][30][31][32] Despite all of these merits,h owever,t hey require ah igh-temperatures intering process to achieve acceptable ionic conductivity.T he high-temperature process not only causesd eleterious reactions between the electrolytes and electrodes and damage to other components, but also makes it difficult to fabricate thin and large-area electrolyte sheets for ASSBs. [28][29][30][31][32] Furthermore, hard and brittle features of the sintered electrolyte sheets inhibitc lose contact betweent he electrolyte and electrode;t hus leading to both poor electrochemical performance and reliability of ASSBs.…”