鈮酸鋰調控固態電解質電場結構促進鋰離子高效傳輸！

聚合物基固態電解質得益于其易加工性，最有希望應用于下一代固態鋰金屬電池。目前，聚合物基態電解質的離子電導率提升策略多為加入導鋰陶瓷以構建離子傳輸通道，其提升程度有限。電場在鋰離子輸運過程中存在重要影響，目前研究中有關電場對鋰離子傳輸的影響機制尚不明確。

近日，清華大學深圳國際研究生院康飛宇教授、賀艷兵副教授和呂偉副教授等人在Science China Materials發表研究論文，將兼具高離子電導率和高介電常數的鈮酸鋰嵌入聚偏氟乙烯基體中，設計了一種新型復合固態電解質。

本文要點

1)鈮酸鋰顆粒有效調節電解質內部電場結構，增強了離子輸運方向電場強度，實現了離子電導率的大幅提升（7.39×10?4 S cm?1，25°C）。

2) 該電解質匹配高鎳正極和鋰金屬負極的固態電池可穩定循環1000次以上，容量保持率為72%。 該研究為設計下一代固態鋰電池用高離子電導復合固態電解質提供了新的策略。



Figure1.Working mechanisms of solid-state NCM811 /Li batteries using NPC and PVDF electrolytes during long cycles. (a) In the NCM811/PVDF/Li batteries, the local aggregation of electric field in PVDF hinders the Li+ uniform transport and promotes Li dendrite growth. (b) In the NCM811/NPC/Li batteries, the enhanced electric field in NPC along the Li-ion transport direction and uniform electric field at the interface with Li metal contribute to fast Li+ conduction and uniform Li platting/stripping.



Figure2.Morphology and physicochemical characterizations of PVDF and NPC electrolytes. Surface SEM image of (a) PVDF and (b) NPC-30 electrolytes. (c) Cross-sectional SEM images of NPC-30 electrolyte. (d) Arrhenius plots of ionic conductivities of PVDF and NPC-based electrolytes. (e) Real part (?r′) of relative permittivity at different frequencies for PVDF and NPC-30 polymer films. AFM morphology images of (f) PVDF and (g) NPC-30 and the corresponding interfacial potential images (h, i).



Figure3.Properties of Li-symmetric cells using PVDF and NPC-30 electrolytes. (a) CCD of the Li/PVDF/Li and Li/NPC-30/Li cells. Cycling curves of Li-symmetrical cells with PVDF and NPC-based electrolytes at current density of (b) 0.1?mA?cm?2, (c) 0.5?mA?cm?2 and (d) 1?mA?cm?2. SEM images of the Li metal surface after cycling at 0.1?mA?cm?2 for 100 h using (e) PVDF and (f) NPC electrolytes. Potential distribution of the cross-section for the interface between Li metal and (g) PVDF, (h) NPC-30 electrolyte from KPFM. (i) 3D ToF-SIMs visual maps of the distributions of LiF+, Li2CO3+ and Li2S+ species at the interface of Li metal after cycling for 100 h using PVDF and NPC-30.



Figure4.Properties of solid-state NCM811/Li solid-state batteries using PVDF and NPC-30 electrolytes. Long-term cycling performance of NCM811/Li cells using PVDF and NPC-30 electrolyte at (a) 0.5?C and (b) 1?C. (c) Rate capacities of NCM811/Li cells using PVDF and NPC-30 electrolyte. (d) Cycling performance of NCM811/Li cells with higher cathode loading of 4?mg?cm?2. Interfacial potential images of (e) NCM811/NPC-30 and (f) NCM/PVDF. Gauss statistic distribution histograms of interfacial potential for (g) NCM811/NPC-30 and (h) NCM811/PVDF. TEM and FFT images of cycled NCM811 cathode with (i) NPC-30 and (j) PVDF in full cells.



Figure5.Characterizations of the ion transport mechanism of PVDF and NPC-30 electrolytes. (a) DFT results for adsorption energies. (b) AFM image and (c) corresponding nano-IR overlap of C=O vibration of DMF at 1663?cm?1. (d) HAADF-TEM image of NPC-30 electrolyte and (e) corresponding EELS mapping of Li element and (f) EDS mapping of Nb element. (g) 6Li NMR spectra of pristine LiNbO3. (h) 6Li NMR spectra of rinsed LiNbO3 from NPC-30 after cycling in the 6Li/NPC-30/6Li cell.

審核編輯：劉清