Positive Electrode Lithium Supplementing Layer for Active Lithium Retention
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Solution Overview
Problem
Secondary batteries face challenges in achieving high first discharge capacity and long cycle life due to the formation of a solid electrolyte interface (SEI) film on the negative electrode during the first charge process, leading to irreversible capacity loss and reduced cycle life.
Innovation Solution
A positive electrode plate with a lithium supplementing layer comprising a lithium-rich metal oxide, a conductive agent, and a binder made from polymers containing specific monomer units is used, which enhances lithium ion release and migration, improving the utilization rate of active lithium and maintaining electron conduction and lithium ion transport performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secondary battery undergoes first charge process, then a SEI film is formed on the negative electrode, but this causes consumption of active ions and irreversible capacity loss
Solution Approach 1:
The patent applies preliminary action by pre-coating the negative electrode with a protective layer before the first charge process. This protective layer is formed in advance to prevent the formation of a thick SEI film that would consume excessive active lithium ions, thereby reducing irreversible capacity loss and improving cycle life
2Loss of substance
If the positive electrode plate uses a lithium supplementing layer with lithium-rich metal oxide, then the utilization rate of active lithium is improved, but the binder may react with active lithium ions causing capacity loss
Solution Approach 1:
The patent applies parameter changes by carefully controlling the pH value of the binder within a specific range (6.0-8.0) and adjusting the molecular weight and chemical composition of the binder. These parameter optimizations prevent excessive reaction between the binder and active lithium ions while maintaining good binding performance, thereby reducing capacity loss and improving cycle life
Solution Approach 2:
The patent applies composite materials by using a composite binder system that combines organic and inorganic components, or by using a copolymer binder with specific functional groups. This composite approach allows the binder to effectively bind the lithium-rich metal oxide particles while minimizing unwanted reactions with active lithium ions, achieving both low capacity loss and long cycle life
3Ease of manufacture
If the binder contains excessive carboxyl groups, then it can consume free lithium compounds, but it may also react with active lithium ions reducing lithium ion release
Solution Approach 1:
The patent applies parameter changes by precisely controlling the carboxyl group content and pH value of the binder within optimal ranges. This balanced parameter selection allows the binder to consume harmful free lithium compounds and provide slurry stability while preventing excessive consumption of active lithium ions, ensuring sufficient lithium ion release during charging
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 results in improved first charge/discharge capacity, energy density, and extended cycle life of secondary batteries by optimizing the lithium supplementing layer's composition and structure, ensuring effective lithium supplementation and reduced loss of active lithium.
Implementation Method 1
the positive electrode lithium supplementing material to release more lithium ions and for the de-intercalated active lithium to migrate to a negative electrode for lithium supplementation
Implementation Method 2
free lithium compounds such as LiGH and Li2CO3 on the surface of the lithium-rich metal oxide can be consumed
Data Source
AI summary
A positive electrode plate is provided. The positive electrode plate comprises a positive electrode current collector, a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and a lithium supplementing layer provided on a surface of the positive electrode active material layer opposite to the positive electrode current collector. The lithium supplementing layer comprises a positive electrode lithium supplementing material, a conductive agent and a binder A, the positive electrode lithium supplementing material comprises a lithium-rich metal oxide, and the binder A is selected from polymers containing a first monomer unit shown by a formula I and a second monomer unit shown by a formula II, where the R1, R2, R3, R4, R5 and R6 are each independently selected from hydrogen or substituted or unsubstituted C1 to C8 alkyl, and the R is selected from substituted or unsubstituted C1 to C8 alkyl.