Mixed-Conducting Anode Protection Films for SEI and Dendrite Control
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Solution Overview
Problem
Lithium-ion batteries face challenges due to volumetric changes and the formation of a solid electrolyte interphase (SEI) at the anode, leading to inefficiencies and safety issues, particularly with lithium metal anodes, which result in reduced energy density and thermal runaway risks.
Innovation Solution
The implementation of protective films, such as Li9Ti5O12 and lithium transition metal dichalcogenides, on lithium metal or graphite anodes to prevent dendrite growth and enhance ion conductivity, reducing SEI formation and overall cell resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid ceramic layer is used to prevent dendrite growth, then safety is improved, but cell resistance increases
Solution Approach 1:
The patent applies composite materials by combining a rigid ceramic layer (such as Al2O3) with a conductive polymer layer (such as polyacetylene, polypyrrole, or polythiophene) to create a protective film that exhibits both mechanical strength for dendrite prevention and electrical conductivity for low resistance. This composite structure resolves the contradiction by integrating the beneficial properties of both materials while eliminating their individual drawbacks.
2Loss of energy
If an electronic conducting layer is used to promote conductivity, then cell resistance is reduced, but dendrite protection is insufficient
Solution Approach 1:
The protective film combines a conductive polymer layer (providing electrical conductivity) with a rigid ceramic layer (providing mechanical strength and dendrite protection). The conductive polymer reduces cell resistance while the ceramic component maintains structural integrity and prevents dendrite growth, thus resolving the contradiction between conductivity and protection.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different layers of the protective film. The conductive polymer layer is optimized for electrical conductivity and is positioned to reduce resistance, while the rigid ceramic layer is optimized for mechanical strength and dendrite prevention. Each layer performs its specific function locally, and together they provide comprehensive protection.
3Quantity of substance
If lithium metal anode is used to increase energy density, then capacity is improved, but SEI formation and dendrite growth increase
Solution Approach 1:
The protective film acts as an intermediary layer between the lithium metal anode and the electrolyte. This intermediate layer prevents direct contact and harmful reactions between the lithium metal and electrolyte, thereby suppressing SEI formation and dendrite growth while allowing the high-capacity lithium metal anode to function, thus resolving the contradiction between energy density and stability.
Solution Approach 2:
The protective film is applied in advance to the lithium metal anode surface before the battery operates. This preliminary protective action prevents the formation of unstable SEI layers and dendrites from the outset, countering the harmful effects before they can develop. The film pre-establishes a stable interface that prevents the runaway reactions associated with unprotected lithium metal anodes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These protective films improve the stability and performance of anodes by reducing SEI formation, enhancing lithium-ion transport, and minimizing volume changes during cycling, thereby increasing energy density and safety while being compatible with existing manufacturing processes.
Implementation Method 1
a rigid ceramic layer, which is ion conducting, is used to prevent the growth of dendrites
Implementation Method 2
Lithium and silicon anodes face challenges arising from volumetric change during battery cycling and formation of solid electrolyte interphase (SEI) due to reactivity with electrolyte
Implementation Method 3
Lithium and silicon anodes face challenges arising from volumetric change during battery cycling
Data Source
AI summary
Interfacial films, which are both electronic conducting and ion conducting, for anode films are provided. The one or more protective films described herein may be mixed conduction materials, which are both electronic conducting and ion-conducting. The one or more protective films described herein may include materials selected from lithium transition metal dichalcogenides, Li9Ti5O12, or a combination thereof. The lithium transition metal dichalcogenide includes a transition metal dichalcogenide having the formula MX2, wherein M is selected from Ti, Mo, or W and X is selected from S, Se, or Te. The transition metal dichalcogenide may be selected from TiS2, MoS2, WS2, or a combination thereof. The lithium transition metal dichalcogenide may be selected from lithium-titanium-disulfide (e.g., LiTiS2), lithium-tungsten-disulfide (e.g., LiWS2), lithium-molybdenum-disulfide (e.g., LiMoS2), or a combination thereof.