Challenges and prospects of high-safety composite separators for lithium-ion batteries

doi:10.19799/j.cnki.2095-4239.2023.0961

Abstract

Abstract:

The separator is a crucial structural component of lithium-ion batteries, responsible for preventing direct contact between the positive and negative electrodes, absorbing and immobilizing electrolyte, and facilitating ion transfer. Commercial separators are currently challenged by issues such as thermal shrinkage at high temperatures, which compromises the long-term safety of the battery. This paper begins with an overview of the requirements for lithium-ion battery separators, including pore structure, electrolyte wettability, and stability-structural, thermal, chemical, and electrochemical-as well as separator-electrolyte interactions. It then reviews recent literature on high-temperature-resistant polymer separators, highlighting research advancements. The focus is on the analysis of strategies for high-heat-resistant polymer-based separators, flame-retardant additive-coated separators, and polymer-substrate composites. The paper discusses the mechanism behind the enhancements provided by flame-retardant multifunctional composite separators and explores strategies for inhibiting lithium dendrite formation through physical barriers, lithium deposition homogenization, and modulation of lithium-ion migration fluxes. Comprehensive analysis indicates that reducing the thickness of polyolefin separators, while integrating high-performance thin coatings, doping with solid electrolytes, and developing high-heat-resistant polymer-based separators, can achieve high ionic conductivity and ensure enhanced safety.

Key words: lithium-ion battery, high safety, composite separators

CLC Number:

TM 911

Guobin ZHONG, Xin YAO, Yongchao LIU, Qian HOU, Hongfa XIANG. Challenges and prospects of high-safety composite separators for lithium-ion batteries[J]. Energy Storage Science and Technology, 2024, 13(6): 1794-1806.

Figures/Tables 10

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序号	参数	要求
1	孔隙率	30%～70%
2	孔径大小	< 1 μm
3	厚度	在力学性能满足的情况尽可能小，< 40 μm
4	渗透率	< 8 (MacMullin =电解液离子电导率/隔膜浸润后离子电导率)
5	机械强度	偏移 < 2% (1000 psi, 1000 psi = 6.895 MPa)
6	穿刺强度	> 300 g/mil (1 mil = 25.4 μm)
7	热稳定性	< 5% (100 ℃，热处理1 h)
8	化学稳定性	不与电解液发生化学反应，耐强氧化、还原环境
9	透气率	200～800 s /100 mL
10	吸液率	一般要求越高越好
11	拉伸强度	一般要求纵向强度达到100 MPa以上，横向强度不能太大

Material	Melting points/℃	Dielectric constant	Material	Melting points/℃	Dielectric constant
PVDF	170	7.25	PTFE	327	2.02
PEEK	343	2.7～3.3	Cellulose	274	3.2
PI	400	3.5	PMMA	160	4.9
PBI	430	3.2	PET	260	3.16
PMIA	460	3.0	PAN	317	3.1
PEI	360	3.3	PPS	300	3.9～5.1

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