Lithium-Ion Cathode Composition With VC-Stabilized SEI
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving a balance between energy density, cycle life, and C-rate performance due to irreversible capacity loss and high reactivity of lithium metal powders, as well as issues with gelation and impedance in existing lithium-supplementing materials.
Innovation Solution
A lithium-ion secondary battery design incorporating a positive electrode plate with a first and second positive electrode material forming a solid solution, along with vinylene carbonate in the electrolyte solution, to create a more uniform and denser solid electrolyte interface (SEI) film, reducing active lithium loss and improving cycle stability and kinetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal powder is used to supplement lithium for the negative electrode, then energy density is improved, but safety deteriorates due to high reactivity and tendency to react with moisture
Solution Approach 1:
The patent introduces a lithium supplementing material containing lithium-containing compound and carbon material as an intermediary substance. The carbon material acts as a protective mediator that prevents direct contact between lithium and moisture, eliminating the safety hazard while maintaining the lithium supplementing function to improve energy density
Solution Approach 2:
The patent creates an inert environment by encapsulating lithium-containing compound within carbon material. This carbon-protected structure provides an inert barrier that prevents lithium from reacting with moisture in the air, solving the safety issue while preserving the active lithium content for energy density enhancement
2Quantity of substance
If Li2NiO2 lithium-supplementing material is used, then lithium content is improved, but processability deteriorates due to gelation of slurry during mixing
Solution Approach 1:
The patent creates a composite material structure where lithium-containing compound is combined with carbon material in specific ratios (0.1-10 wt% carbon). This composite structure prevents gelation during slurry mixing while maintaining high lithium content, thereby improving both lithium supplementation and processability
Solution Approach 2:
The patent optimizes the composition parameters by controlling the content of carbon material within specific ranges (0.1-10 wt% of total mass). This parameter adjustment prevents excessive free lithium on the surface that causes gelation, while maintaining sufficient lithium content for supplementation
3Reliability
If positive electrode lithium supplementation is used, then safety is improved, but cycle life deteriorates due to high decomposition potential and generation of oxygen by-products
Solution Approach 1:
The patent modifies the decomposition potential parameter by selecting specific lithium-containing compounds with lower decomposition potentials than conventional materials. This parameter change enables lithium supplementation while reducing oxygen evolution, thereby improving both safety and cycle life
Solution Approach 2:
The patent applies local quality enhancement by using carbon material to locally protect and stabilize the lithium-containing compound at the positive electrode. This localized protection prevents unwanted reactions and by-product generation, improving cycle life while maintaining safety benefits
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, extended cycle life, and improved C-rate performance by compensating for active lithium loss and stabilizing the SEI film, while reducing structural disruptions and impedance.
Implementation Method 1
During a first charge-discharge cycle of a lithium-ion secondary battery, a solid electrolyte interface (SEI) is formed on a surface of a negative electrode of the battery
Implementation Method 2
a first positive electrode material and a second positive electrode material which forms a solid solution
Data Source
AI summary
A lithium-ion secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte solution. The positive electrode plate includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a first positive electrode material having formula Li1+xFeyMnzM1-y-zPO4-tAt and a second positive electrode material having formula Li2+rNi0.5-qCu0.5-qTivNp+q-vO2-sBs. The electrolyte solution includes vinylene carbonate. A content of the vinylene carbonate based on a total mass of the electrolyte solution is 0.1 wt % to 5 wt %. M includes one or more of Ti, Zr, V, or Cr; A includes one or more of S, N, F, Cl, or Br; −0.1≤x<0.1, 0<y≤1, 0≤z<1, 0<y+z≤1, and 0≤t<0.2.