Lithium Metal Battery Additive Suppressing Dendrite Growth
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Solution Overview
Problem
Existing secondary batteries, including lithium ion and lithium metal secondary batteries, suffer from insufficient energy density and cycle characteristics due to issues like dendrite formation and the need for high mechanical pressure, which compromises their performance and safety.
Innovation Solution
A lithium secondary battery design that deposits lithium metal on the negative electrode without an active material, using an additive to inhibit anisotropic crystal growth, thereby improving energy density and cycle characteristics by suppressing dendrite formation and reducing the need for mechanical pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal is deposited on the negative electrode surface to achieve high energy density, then energy density is improved, but dendrites form on the surface after repeated charging and discharging, causing short-circuiting and capacity loss
Solution Approach 1:
A separator is introduced as an intermediary component between the positive and negative electrodes. This separator physically prevents dendrite-induced short-circuiting while allowing lithium ion transport, thus resolving the contradiction between achieving high energy density through lithium metal deposition and maintaining reliability by preventing dendrite-related failures
Solution Approach 2:
An ultrathin separator film is used to minimize the volume occupied by the separator while maintaining its protective function. This thin film structure allows the battery to achieve high energy density by maximizing the active material content while still preventing dendrite penetration and short-circuiting, thus resolving the contradiction between energy density and cycle characteristics
2Reliability
If a large amount of physical pressure is applied to suppress discrete growth during lithium metal precipitation, then cycle characteristics are improved, but the weight and volume of the battery increase, decreasing energy density
Solution Approach 1:
The mechanical pressure system is replaced with a chemical solution system. Instead of applying continuous mechanical pressure to suppress dendrite growth, the patent uses a specifically formulated electrolyte solution that chemically inhibits anisotropic crystal growth of lithium metal during deposition, thereby resolving the contradiction between improving cycle characteristics and maintaining high energy density
3Reliability
If an additive is added to inhibit anisotropic crystal growth of lithium metal, then cycle characteristics are improved by suppressing dendrite formation, but the complexity of the electrolyte composition increases
Solution Approach 1:
The electrolyte composition parameters are optimized to achieve the desired effect. By carefully controlling the concentration ratios of different components (cyclic carbonate 10-30 vol%, chain carbonate 70-90 vol%, lithium salt 0.5-2 mol/L), the additive effectively suppresses dendrite formation while maintaining manageable electrolyte complexity and ensuring high ionic conductivity
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
The battery achieves high energy density and excellent cycle characteristics by preventing dendrite growth and eliminating the requirement for high mechanical pressure, enhancing both performance and safety.
Implementation Method 1
charging and discharging are performed by depositing lithium metal on the surface of the negative electrode
Implementation Method 2
charging and discharging are performed by depositing lithium metal on the surface of the negative electrode and electrolytically dissolving the deposited lithium
Data Source
AI summary
A lithium secondary battery is provided that has high energy density and excellent cycle characteristics. This lithium secondary battery includes: a positive electrode; a separator or a solid electrolyte; a negative electrode that is free of a negative electrode active material; and optionally, an electrolytic solution, wherein charging and discharging are performed by depositing lithium metal on the surface of the negative electrode and electrolytically dissolving the deposited lithium, and the lithium secondary battery includes an additive that inhibits anisotropic crystal growth of the lithium metal by being codeposited with the lithium metal during charging.