Lithium Power Storage Element with Optimized Positive Electrode Pore Structure
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Solution Overview
Problem
Current nonaqueous lithium power storage elements face challenges in achieving high energy density, high input/output characteristics, and high load charge/discharge cycle durability, with existing methods often compromising on one aspect to improve another.
Innovation Solution
A nonaqueous lithium power storage element design featuring a positive electrode with a carbon-based active material and optimized pore structure, including specific ranges for mesopore and micropore volumes, specific surface area, and pore distribution, combined with a predoped negative electrode, to enhance lithium ion conductivity and electrolyte retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electrical double layer capacitors with activated carbon electrodes are used to achieve high output characteristics, then output reaches 0.5 to 1 kW/L and durability is high, but energy density is limited to 1 to 5 Wh/L
Solution Approach 1:
The patent employs a composite electrode structure combining activated carbon (for high output and durability) with lithium ion battery materials (for high energy density). This composite approach allows the device to achieve both high output characteristics and high energy density simultaneously, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent applies different material properties to different regions of the electrode system. The positive electrode uses activated carbon optimized for high output and durability, while the negative electrode uses lithium ion battery materials optimized for high energy density. This local differentiation allows each electrode to contribute its strength, resolving the overall contradiction.
2Quantity of substance
If lithium ion batteries are designed for high energy density, then energy density exceeds 100 Wh/L, but output characteristic decreases to 3 kW/L or lower and durability becomes inferior
Solution Approach 1:
The patent creates a hybrid system that combines lithium ion battery technology (providing high energy density) with electrical double layer capacitor technology (providing high output). This composite structure enables the device to achieve both high energy density and high output characteristics, resolving the contradiction between these parameters.
3Quantity of substance
If lithium ion batteries operate at high depth of discharge to maximize capacity utilization, then usable capacity increases, but cycle durability and high-temperature storage characteristics deteriorate
Solution Approach 1:
The patent introduces an intermediary mechanism where the activated carbon electrode acts as a buffer that can accept and release lithium ions rapidly without the degradation issues of traditional lithium ion battery materials. This intermediary structure allows high depth of discharge operation while protecting the overall system durability.
Solution Approach 2:
The patent changes the operational parameters of the positive electrode by using activated carbon with specific pore size distributions (mesopores and micropores) that enable rapid ion transport. This parameter optimization allows the electrode to operate at high depths of discharge while maintaining durability through its unique structural properties.
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 solution achieves a balance of high energy density, high input/output characteristics, and improved durability, allowing for efficient charge/discharge cycles without restrictions on depth of discharge.
Implementation Method 1
charge/discharge is accomplished by: non-Faraday reaction by adsorption/desorption of anions similar to an electrical double layer capacitor at about 3 V or higher, at the positive electrode
Implementation Method 2
Faraday reaction by intercalation/release of lithium ions similar to a lithium ion battery, at the negative electrode
Data Source
AI summary
This nonaqueous lithium power storage element contains a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte that contains lithium ions. The positive electrode has a positive electrode current collector and a positive electrode active material layer disposed on one surface or both surfaces of the positive electrode current collector, and the positive electrode active material layer contains a positive electrode active material that contains a carbon material. The negative electrode has a negative electrode current collector and a negative electrode active material layer disposed on one surface or both surfaces of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material capable of occluding and releasing the lithium ions. When the pore distribution of the positive electrode active material layer is measured by mercury intrusion, the pore distribution curve for the relationship between the pore diameter and log differential pore volume has at least one peak having a peak value of 1.0-5.0 mL/g for the log differential pore volume in the pore diameter range of 0.1-50 µm, and the total cumulative pore volume Vp in the pore diameter range of 0.1-50 µm is 0.7-3.0 mL/g.