Nickel-Rich Li-Ion Cathode and FEC Electrolyte for Cycle Stability
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Solution Overview
Problem
Existing lithium-ion batteries face challenges in achieving high energy density, good C-rate performance, and long cycle life due to irreversible capacity loss during the first charge-discharge cycle, particularly with high-specific-capacity negative electrode materials, and existing lithium supplementation methods pose safety hazards or reduce battery life.
Innovation Solution
The electrochemical device incorporates a nickel-based positive active material with specific resistance, compaction density, and areal density parameters, along with an electrolyte solution containing fluoroethylene carbonate, forming a homogeneous SEI film to supplement lithium and improve electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metallic lithium powder is used to supplement lithium in the negative electrode, then energy density is improved, but safety hazards increase due to high reactivity with moisture
Solution Approach 1:
The patent uses a lithium supplementing agent containing lithium compound and carbon material as an intermediary substance. The lithium compound (such as lithium carbonate, lithium hydroxide, or lithium oxide) combined with carbon material serves as a safer alternative to metallic lithium powder, reducing reactivity with moisture while still providing lithium supplementation. The carbon material acts as a carrier that moderates the reactivity of the lithium compound.
Solution Approach 2:
The patent changes the chemical form of lithium from metallic lithium (highly reactive) to lithium compounds (lower reactivity) such as lithium carbonate, lithium hydroxide, or lithium oxide. This parameter change in the chemical state of lithium reduces its reactivity with moisture and air, thereby improving safety while maintaining the ability to supplement active lithium source.
2Stability of the object's composition
If stabilized lithium metal powder is used, then stability is improved, but production process complexity increases due to strict moisture control requirements
Solution Approach 1:
The carbon material in the lithium supplementing agent serves as an intermediary that protects the lithium compound from direct exposure to moisture and air. This combination reduces the stringency of moisture control requirements compared to using stabilized lithium metal powder, while still providing adequate stability during production and storage.
Solution Approach 2:
The patent uses a composite material consisting of lithium compound and carbon material. This composite structure provides both stability and ease of handling, reducing the complexity of production process control while maintaining adequate stability. The carbon material matrix protects the lithium compound and facilitates easier processing.
3Ease of operation
If lithium-oxygen compound is used for positive electrode lithium supplementation, then ease of operation is improved, but battery life decreases due to decomposition generating oxygen and by-products
Solution Approach 1:
The patent changes the decomposition characteristics of the lithium supplementing material by using lithium compounds with lower decomposition potentials and no oxygen evolution. The selected lithium compounds (carbonate, hydroxide, oxide) decompose without generating oxygen or harmful by-products, thereby extending battery life while maintaining ease of operation.
Solution Approach 2:
The patent converts the potential harm of decomposition by-products into a benefit by selecting lithium compounds that decompose cleanly without generating oxygen or harmful substances. The decomposition products are benign and do not adversely affect battery performance or life, turning a potential problem into an advantage.
4Power
If Li2NiO2 lithium-supplementing material is used, then specific capacity is improved, but energy density decreases due to residual inactive constituents
Solution Approach 1:
The patent extracts and eliminates the problematic residual inactive constituents by selecting lithium compounds that fully decompose or react without leaving residual materials on the electrode. The lithium carbonate, lithium hydroxide, or lithium oxide used in the supplementing agent decompose completely or react fully, leaving no inactive residues that would reduce energy density.
Solution Approach 2:
The patent changes the decomposition behavior of the lithium supplementing material by selecting compounds with appropriate decomposition characteristics. The chosen lithium compounds decompose at temperatures and conditions that ensure complete reaction without leaving residual inactive constituents, thereby maintaining both high specific capacity and high energy density.
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 device achieves high energy density, good C-rate performance, and extended cycle life by optimizing positive electrode parameters and using fluoroethylene carbonate to form a dense SEI film, reducing continuous lithium depletion and enhancing cycle stability.
Implementation Method 1
During a first charge-discharge cycle of a lithium-ion battery, a solid electrolyte interface (SEI) is formed on a surface of a negative electrode of the battery
Implementation Method 2
the solvent in an electrolyte solution continues a reduction reaction on the negative electrode
Data Source
AI summary
An electrochemical device includes a positive electrode, a negative electrode, a separator, and an electrolyte solution. The positive electrode includes a positive active material layer. The positive active material layer includes a positive active material represented by Formula (1): Li1+rNi1-p-qM1pM2qO2-sM3s Formula (1). In Formula (1), 0<r≤1, 0<p<1, 0<q<1, 0<p+q<0.5, 0≤s<0.2, M1 and M2 each are independently at least one of Co, Mn, Fe, Ti, Al, V, Cr, Nb, Zr, La, or Y, and M3 is at least one of S, N, F, Cl, or Br. A resistance of the positive electrode is R Ω. A compaction density of the positive electrode is P g/cm3. A single-side areal density of the positive electrode is Q g/1540.25 mm2. The positive electrode satisfies Formula (2): 3.5≤R·P/Q≤30 Formula (2). The electrolyte solution includes fluoroethylene carbonate.