Hollow Carbon Negative Electrode for Li-Ion Battery Resistance Control
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Solution Overview
Problem
Lithium ion secondary batteries using high-concentration nonaqueous electrolyte solutions face increased resistance due to salt concentration unevenness, which is exacerbated by the difficulty of lithium ions reaching the negative electrode active material layer and electrolyte solution drainage during charging and discharging.
Innovation Solution
Incorporating hollow particles with a carbon material shell and a hollow portion containing a nonaqueous electrolyte solution, where the proportion of Li in the hollow portion is 32% or higher, to facilitate lithium ion movement and maintain even salt concentration, thereby suppressing resistance increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high-concentration nonaqueous electrolyte solution is used, then ion density increases, but viscosity increases and lithium ion transport becomes difficult
Solution Approach 1:
The negative electrode active material is divided into hollow particles with internal cavities. These hollow portions act as reservoirs that segment the electrolyte storage function from the electrode structure, allowing concentrated electrolyte to be stored within the particles themselves rather than relying solely on external electrolyte transport through the electrode layer.
Solution Approach 2:
The hollow portion is nested within the shell portion of the hollow particles. The shell made of carbon material contains the high-concentration electrolyte solution within its hollow interior, creating a nested structure where the electrolyte reservoir is embedded within the electrode particle structure.
2Quantity of substance
If a high-concentration nonaqueous electrolyte solution is used, then ion density increases, but salt concentration unevenness occurs in the thickness direction
Solution Approach 1:
The hollow particles are distributed throughout the negative electrode active material layer, creating local electrolyte reservoirs at multiple positions within the electrode thickness. This local distribution of electrolyte-containing hollow particles ensures that salt concentration remains relatively uniform across the electrode thickness, preventing concentration gradients that would otherwise form with high-concentration electrolytes.
3Quantity of substance
If the nonaqueous electrolyte solution is used with high-concentration electrolyte salt, then ion density increases, but the electrolyte solution drains out during expansion and contraction
Solution Approach 1:
The hollow portions within the hollow particles are pre-filled with nonaqueous electrolyte solution before battery assembly. This internal reservoir structure provides a buffer that compensates for electrolyte drainage during electrode expansion and contraction cycles, maintaining adequate electrolyte levels without requiring excessive initial electrolyte filling.
4Reliability
If hollow particles with high Li proportion are used, then resistance increases are suppressed, but device complexity increases
Solution Approach 1:
The hollow particles serve multiple functions simultaneously: they act as the negative electrode active material, provide internal reservoirs for electrolyte storage, and maintain structural integrity during volume changes. This self-service approach integrates multiple functions into a single component type, reducing overall device complexity despite the advanced functionality provided.
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
This configuration effectively reduces resistance and prevents metallic lithium precipitation, even with high-concentration electrolyte solutions, by ensuring consistent lithium ion distribution and improved electrolyte retention within the battery.
Implementation Method 1
a nonaqueous electrolyte solution contained in a hollow portion formed in the interior of the shell portion
Implementation Method 2
The nonaqueous electrolyte solution contains a lithium salt as an electrolyte salt
Data Source
AI summary
Provided is a lithium ion secondary battery in which increases in resistance upon repeated charging and discharging are suppressed even when using a high-concentration nonaqueous electrolyte solution. The lithium ion secondary battery disclosed herein has an electrode body having a positive electrode and a negative electrode, and a nonaqueous electrolyte solution. The negative electrode has a negative electrode active material layer containing a negative electrode active material. The negative electrode active material includes hollow particles having a shell portion made up of a carbon material and a hollow portion formed in the interior of the shell portion. The hollow portion of the hollow particles contains a nonaqueous electrolyte solution. The proportion of the amount of Li in the hollow portion of the hollow particles relative to the amount of Li necessary for charging and discharging the lithium ion secondary battery is 32% or higher.