Negative Electrode Structure for High-Rate Secondary Batteries
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Solution Overview
Problem
Secondary batteries face challenges in achieving high rate capability without compromising energy density, as high energy density requires higher material press density, while high rate discharge performance necessitates lower material press density and more conductive materials to prevent performance decline due to high temperature and lithium precipitation.
Innovation Solution
A secondary battery design with a negative electrode plate featuring a carbon-based active material with controlled grain size and non-Faraday capacitance, optimized pore volume, and surface coating, which enhances ion and electron conduction, reducing charge transmission resistance and improving rate capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If higher material press density is used to increase energy density, then energy density is improved, but rate discharge performance deteriorates due to reduced ion and electron conduction
Solution Approach 1:
The patent applies parameter changes by precisely controlling the grain size of carbon material particles within a specific range (0.01-6 nm) and optimizing the non-Faraday capacitance (0.05-10 nF). These parameter adjustments enable the negative electrode to achieve both high material press density for energy density and sufficient ion/electron conduction for rate discharge performance, resolving the contradiction between the two requirements.
Solution Approach 2:
The patent utilizes porous materials by optimizing the pore volume of the negative electrode active material (0.001-0.5 cm³/g). The controlled porosity provides pathways for ion transport while maintaining high material density, thus improving both energy density and rate discharge performance simultaneously by balancing material packing efficiency with ion conduction channels.
2Power
If more conductive materials and thicker current collectors are used to improve rate discharge performance, then rate capability is improved, but energy density deteriorates due to increased auxiliary material content
Solution Approach 1:
The patent changes the critical parameter of carbon material grain size to a very small range (0.01-6 nm), which fundamentally improves intrinsic conductivity at the nanoscale. This eliminates the need for excessive conductive additives and thick current collectors, as the nanoscale carbon particles themselves provide sufficient conduction pathways, thus improving rate discharge performance without sacrificing energy density.
Solution Approach 2:
The patent employs composite materials by creating a optimized composite structure of carbon material particles with specific grain size and pore volume characteristics. This composite design achieves high conductivity and energy density simultaneously through the synergistic effect of controlled particle size, pore structure, and non-Faraday capacitance, avoiding the need for separate conductive material additives.
3Quantity of substance
If higher material press density is used to increase energy density, then cycle performance deteriorates due to high temperature effects and lithium precipitation
Solution Approach 1:
The patent applies parameter changes by controlling carbon material grain size (0.01-6 nm) and pore volume (0.001-0.5 cm³/g) to optimize the electrode structure. The small grain size and controlled porosity facilitate efficient lithium ion insertion/extraction and heat dissipation, preventing lithium precipitation and high-temperature degradation even at high material press density, thus maintaining both energy density and cycle performance.
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 optimized design significantly enhances the rate capability of the secondary battery by increasing electrochemical active sites, accelerating ion-electron transmission, and reducing charge resistance, while maintaining energy density and cycle performance.
Implementation Method 1
a non-Faraday capacitance of the negative electrode plate is Cdl nF, satisfying 0.05≤Cdl≤10; 0.1≤√{square root over (Cdl−XS)}≤3
Data Source
AI summary
Disclosed are a secondary battery and a battery pack including the secondary battery. The secondary battery includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material. A grain size of the negative electrode active material is XS nm, a non-Faraday capacitance of the negative electrode plate is Cdl nF, satisfying 0.05≤Cdl≤10, and a relationship of the grain size XS and the non-Faraday capacitance Cdl satisfies 0.1≤√{square root over (Cdl-XS)}≤3.