Hybrid Lithium Power Storage Element Design
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Solution Overview
Problem
Nonaqueous lithium power storage elements face challenges with thermal runaway during internal short circuiting, increased resistance during high-load charge/discharge cycling, and gas generation due to lithium compound decomposition under high-temperature conditions, while requiring high energy density and durability.
Innovation Solution
A nonaqueous lithium power storage element design featuring a positive electrode with a lithium compound, a negative electrode capable of intercalating lithium ions, and a specific coating configuration to suppress thermal runaway and resistance increase, with a lithium ion-containing nonaqueous electrolytic solution, and a negative electrode active material with controlled doping and surface area to enhance energy density and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium ion batteries are designed for high output exceeding 3 kW/L, then output characteristic is improved, but energy density decreases to 100 Wh/L or lower and durability becomes inferior
Solution Approach 1:
The invention divides the power storage system into two distinct electrodes: a positive electrode using activated carbon for non-Faraday reactions (providing high output and durability) and a negative electrode using lithium ion intercalation materials for Faraday reactions (providing high energy density). This segmentation allows each electrode to optimize its function independently, resolving the contradiction between output and durability.
Solution Approach 2:
The invention creates a hybrid power storage element that combines characteristics of electrical double layer capacitors (positive electrode with activated carbon) and lithium ion batteries (negative electrode with lithium ion intercalation). This composite approach integrates the high output/durability of capacitors with the high energy density of batteries, achieving all three requirements simultaneously.
2Reliability
If lithium ion batteries are used with depth of discharge restricted to 0-100% range, then durability is improved, but usable capacity becomes lower
Solution Approach 1:
The invention pre-dopes the negative electrode with lithium ions during manufacturing, creating a lithium ion-rich negative electrode. This preliminary action ensures that the negative electrode has sufficient lithium ion reservoir to fully utilize the positive electrode's capacity without causing degradation, allowing 0-100% depth of discharge while maintaining durability.
3Power
If electrical double layer capacitors use activated carbon in both electrodes, then high output and high durability are achieved, but energy density remains low at 1-5 Wh/L
Solution Approach 1:
The invention applies different material qualities to different electrodes: the positive electrode uses activated carbon with high surface area for non-Faraday reactions (optimizing for output and durability), while the negative electrode uses lithium ion intercalation materials with high lithium ion capacity (optimizing for energy density). This local differentiation resolves the energy density limitation.
4Quantity of substance
If nonaqueous lithium power storage elements use lithium compound in positive electrode, then high energy density is achieved, but thermal runaway occurs during internal short circuiting and gas generation occurs under high-temperature conditions
Solution Approach 1:
The invention reverses the conventional configuration by placing lithium compound in the negative electrode instead of the positive electrode. This converts the harmful effect (lithium compound decomposition at high temperature) into a beneficial arrangement where the lithium compound is protected by the negative electrode structure and operates at lower potentials, eliminating thermal runaway and gas generation while maintaining high energy density.
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 effectively suppresses thermal runaway and resistance increase, maintains high energy density, and ensures high-load charge/discharge cycle characteristics, reducing gas generation and improving durability under high-temperature conditions.
Implementation Method 1
Faraday reaction by intercalation and release of lithium ions similar to a lithium ion battery, at the negative electrode
Implementation Method 2
non-Faraday reaction by adsorption and desorption of anions similar to an electrical double layer capacitor at about 3 V or higher, at the positive electrode
Implementation Method 3
a lithium ion-containing nonaqueous electrolytic solution
Data Source
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AI summary
A lithium storage element contains a positive electrode that contains a lithium compound other than an active material, a negative electrode, a separator, and a nonaqueous electrolytic solution containing lithium ions, for which an active material is applied on both surfaces of a nonporous positive electrode power collector, and a negative electrode active material capable of storing and releasing lithium ions is applied on both surfaces of a nonporous negative electrode power collector. The relationships 0.85 ≤ Cx1/Cy1 ≤ 1.15, 0.85 ≤ Ax1/Ay1 ≤ 1.15, 0.80 ≤ (Ax1 + Cx1)/(Ay1 + Cy1) ≤ 1.20, 0.1 ≤ Cx2 (g/m2) ≤ 18, 0.1 ≤ Cy2 (g/m2) ≤ 18, 0.60 ≤ Cy2/Cx2 ≤ 1.70, and 0.60 ≤ Cx2/Cy2 ≤ 1.70 are satisfied, where Cx1 is the basis weight of the positive electrode active material layer Cx surface, Cy1 is the basis weight of the other positive electrode active material layer Cy surface, Ay1 is the basis weight of the negative electrode active material layer Ay surface facing opposite the Cy surface, Ax1 is the basis weight of the other negative electrode active material layer Ax surface, Cx2 is the lithium compound amount per area of the Cx surface, and Cy2 is the lithium compound amount per area of the Cy surface.