Core-Shell Gradient Cathode and CNT-Si Anode for Li-Ion Batteries
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving high energy density, safety, and cycle life due to issues with Ni-enriched NMC cathodes and silicon anodes, which experience volume changes, electrical contact loss, and rapid capacity fading.
Innovation Solution
A high-energy density rechargeable Li-ion battery cell is developed using a core-shell gradient or concentration gradient nickel-based lithium metal oxide cathode combined with a composite anode of nanoporous silicon encapsulated by carbon nanotubes, enhancing both energy and power density while improving cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni-enriched NMC cathode materials are used to increase energy density, then capacity and rate capability are improved, but lifetime and safety deteriorate due to parasitic side reactions with electrolyte
Solution Approach 1:
The patent uses composite cathode materials combining Ni-enriched NMC with other metal oxides (such as Al, Ti, Zr) to create a composite structure that maintains high capacity while improving stability. The composite approach allows the beneficial high-energy-density properties of Ni-rich materials to be retained while the additional materials suppress parasitic reactions and improve cycle life.
Solution Approach 2:
The patent implements surface modification techniques that create different compositions or structures at the surface versus the bulk of the cathode particles. This local quality differentiation allows the bulk to maintain high Ni content for energy density while the surface is optimized for stability and reduced electrolyte interaction.
2Quantity of substance
If Si anode material is used to achieve high gravimetric capacity, then energy density is improved, but cycle life deteriorates due to volume change and pulverization
Solution Approach 1:
The patent encapsulates Si particles within a protective matrix or shell structure, creating a nested configuration where the Si core provides high capacity while the surrounding matrix accommodates volume expansion and prevents pulverization. This nested structure allows the Si to maintain electrical contact throughout cycling.
Solution Approach 2:
The patent employs flexible protective shells or coatings around Si anode particles that can accommodate the significant volume changes during lithiation and delithiation. These flexible structures prevent mechanical failure and maintain electrical connectivity, thereby improving cycle life while preserving the high capacity of Si.
3Quantity of substance
If higher cut-off voltages and high electrode packing densities are pursued to increase energy density, then capacity is improved, but lifetime and safety of Ni-enriched NMC cathodes deteriorate
Solution Approach 1:
The patent modifies key parameters of the cathode materials including composition ratios, particle size distribution, and surface properties to optimize performance. By adjusting these parameters, the cathode can operate at higher voltages and densities while maintaining stability and reducing parasitic reactions.
Solution Approach 2:
The patent creates composite cathode structures that combine Ni-enriched NMC with stabilizing materials, enabling the system to withstand higher operating voltages and packing densities without suffering from increased parasitic side reactions. The composite structure distributes stress and reduces localized degradation.
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 life, meeting the requirements for electric vehicle applications with improved stability and capacity retention, outperforming standard NCA cathodes in terms of capacity retention and rate capability.
Implementation Method 1
The lithium ions move through an electrolyte from the negative electrode (anode) to the positive electrode (cathode) during discharge, and in reverse, from the positive electrode (cathode) to the negative electrode (anode), during recharge.
Implementation Method 2
The anode is typically composed of lithium, dissolved as ions, into a carbon or in some cases metallic lithium.
Implementation Method 3
The cathode material is made up from lithium liberating compounds, typically electro-active oxide materials.
Data Source
AI summary
A high energy density lithium-ion rechargeable battery cell is provided which includes an anode material containing a carbon-nanotube (CNT)-Si composite and a cathode material containing a core-shell gradient and/or concentration gradient nickel-based lithium metal oxide.