Lithium Battery Anode Dissolution Layer for Safe Pre-Lithiation
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Solution Overview
Problem
Lithium secondary batteries face challenges with silicon-based negative electrodes due to volume changes during lithium ion intercalation/de-intercalation, leading to mechanical instability, impaired cycle characteristics, and high initial irreversible capacity, along with safety concerns in existing pre-lithiation methods such as lithium metal transfer and electrochemical processes.
Innovation Solution
A negative electrode for lithium secondary batteries is developed with a specific electrolyte solution dissolution layer having a thickness of 0.1 μm to 5 μm and including a binder copolymer with a fluoro group, which allows for uniform pre-lithiation without lithium loss by dissolving in the electrolyte solution after assembly, reducing side reactions and enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to improve capacity, then discharge capacity is improved, but volume change during lithium ion intercalation/de-intercalation causes mechanical instability and impaired cycle characteristics
Solution Approach 1:
A lithium transfer layer is introduced as an intermediary between the silicon-based negative electrode active material and the external environment. This layer mediates the lithium ion intercalation/de-intercalation process, allowing lithium ions to pass through while preventing direct contact that would cause mechanical instability. The layer acts as a buffer that accommodates volume changes without compromising the structural integrity of the silicon particles.
Solution Approach 2:
The lithium transfer layer is implemented as a thin film structure that can flexibly accommodate the volume expansion and contraction of silicon particles during charging and discharging cycles. This thin film maintains mechanical stability while allowing ionic transport, solving the contradiction between high capacity utilization and mechanical stability.
2Quantity of substance
If silicon-based negative electrode active material is used to improve capacity, then discharge capacity is improved, but initial irreversible capacity becomes large due to volume change and surface side reactions
Solution Approach 1:
The lithium transfer layer serves as a protective intermediary that prevents direct exposure of silicon-based active material to the electrolyte solution. This mediation suppresses surface side reactions such as electrolyte decomposition and solid electrolyte interface (SEI) formation on silicon surfaces, thereby reducing initial irreversible capacity loss while still enabling efficient lithium ion transport.
Solution Approach 2:
The lithium transfer layer creates an inert environment around the silicon-based active material, isolating it from reactive components in the electrolyte solution. This inert barrier prevents harmful surface reactions that would otherwise consume lithium ions irreversibly during the initial charging cycles.
3Loss of substance
If existing pre-lithiation methods such as lithium metal transfer are used to reduce initial irreversible capacity, then lithium loss is reduced, but safety concerns arise due to fire and explosion risks
Solution Approach 1:
The lithium transfer layer is designed as a disposable protective layer that is consumed during the initial lithium transfer process. This layer sacrificially reacts with lithium ions during pre-lithiation, protecting the main silicon-based active material from irreversible reactions later. The layer is intentionally designed to be consumed in a controlled manner during initial cycles, improving overall battery efficiency without compromising safety.
Solution Approach 2:
The invention replaces the mechanical handling of lithium metal (which poses safety risks) with a chemical/ionic transfer mechanism through the lithium transfer layer. Instead of physically transferring lithium metal that could cause fire or explosion, the system uses ionic diffusion through the layer, which is inherently safer and more controllable while achieving the same pre-lithiation effect.
4Loss of substance
If existing electrochemical pre-lithiation method is used to reduce initial irreversible capacity, then lithium loss is reduced, but production costs increase
Solution Approach 1:
The lithium transfer layer is incorporated into the electrode structure during the initial manufacturing process, performing the pre-lithiation function beforehand. This preliminary action eliminates the need for separate, costly electrochemical pre-lithiation steps that would require additional equipment, time, and energy. The pre-lithiation effect is achieved as an integral part of electrode fabrication, reducing overall production costs.
Solution Approach 2:
The invention merges the pre-lithiation function with the electrode manufacturing process itself. The lithium transfer layer is formed and integrated during standard electrode fabrication, combining multiple functions (structural support, lithium ion transport, and pre-lithiation) into a single integrated component, thereby eliminating the need for separate pre-lithiation processing steps and reducing production costs.
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 solution enables efficient and uniform pre-lithiation of the negative electrode active material layer, reducing lithium loss and maintaining battery capacity and cycle stability, while ensuring safety by avoiding direct contact with the reactive lithium metal.
Implementation Method 1
an electrolyte solution dissolution layer having a thickness of 0.1 μm or more and 5 μm or less and including a binder copolymer including a monomer including a fluoro group
Implementation Method 2
a negative electrode active material layer formed on one surface or both surfaces of the negative electrode current collector layer
Data Source
AI summary
A negative electrode for a lithium secondary battery, a method for manufacturing a lithium secondary battery, and a lithium secondary battery are disclosed. The negative electrode includes a negative electrode current collector; a negative electrode active material layer on one surface or both surfaces of the current collector; and an electrolyte solution dissolution layer on a surface of the negative electrode active material layer opposite to a surface of the negative electrode active material layer facing the negative electrode current collector layer. The electrolyte solution dissolution layer has a thickness of 0.1 μm or more and 5 μm or less. The electrolyte solution dissolution layer comprises a binder copolymer comprising a monomer unit comprising a fluoro group, and the monomer unit is present in an amount of 5 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the binder copolymer.