Solid-State Battery Anode Capacity Ratio for Dendrite Suppression
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Solution Overview
Problem
Lithium dendrite formation in all-solid-state secondary batteries with lithium as an anode active material leads to reduced capacity and short circuits, necessitating an improved anode active material and charging method.
Innovation Solution
An all-solid-state secondary battery configuration with an anode active material layer that includes materials alloyable with lithium, a binder for stability, and a metal layer formed during charging, which acts as a protective layer to inhibit dendrite growth and enhance energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium is used as an anode active material to increase energy density, then energy density is improved, but lithium dendrite formation occurs causing short circuits and capacity reduction
Solution Approach 1:
A metal layer is introduced as an intermediary between the solid electrolyte and the anode active material layer. This metal layer acts as a buffer that prevents direct contact and potential dendrite formation while still allowing lithium ion transport, thus maintaining high energy density while improving safety and preventing short circuits.
Solution Approach 2:
The anode structure is designed as a composite system comprising multiple layers: a solid electrolyte layer, a metal layer, and an anode active material layer. This composite structure combines the high capacity of lithium-based materials with the protective properties of the metal layer, achieving both high energy density and enhanced reliability through synergistic material combination.
2Volume of moving object
If lithium is used as an anode active material to reduce battery size, then volume and weight are reduced, but dendrite formation leads to capacity reduction
Solution Approach 1:
The metal layer serves as an intermediary that prevents dendrite-induced capacity loss while maintaining the compact structure. By blocking dendrite penetration into the anode active material, the metal layer preserves the functional capacity of the battery without increasing its volume, thus resolving the contradiction between miniaturization and capacity maintenance.
3Reliability
If a metal layer is formed during charging to act as a protective layer, then dendrite growth is inhibited, but device structure becomes more complex
Solution Approach 1:
The metal layer is formed by controlling the charging process parameters, specifically by charging to a voltage that exceeds the initial charge capacity of the anode active material layer. This parameter-based formation approach allows the metal layer to self-organize as a protective structure without requiring additional manufacturing steps or complex device design, thus achieving dendrite inhibition while minimizing structural complexity.
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 prevents short circuits and capacity reduction by stabilizing the anode active material layer and utilizing the metal layer as a lithium reservoir, thereby enhancing the battery's energy density and cycle stability.
Implementation Method 1
the anode active material layer includes an anode active material which is alloyable with lithium or forms a compound with lithium
Implementation Method 2
lithium may be incorporated into the anode active material layer at the initial stage of charging
Implementation Method 3
After the initial charge capacity of the anode active material layer is exceeded, lithium is deposited on a rear surface of the anode active material layer. A metal layer may be formed by the deposited lithium.
Implementation Method 4
During discharge, lithium of the anode active material layer and the metal layer may be ionized and transferred towards the cathode
Implementation Method 5
lithium of the anode active material layer and the metal layer may be ionized and transferred towards the cathode
Implementation Method 6
the anode active material layer may cover the metal layer, and thus may act as a protective layer for the metal layer, and also the anode active material layer may inhibit the deposition and growth of a dendrite
Data Source
AI summary
An all-solid-state secondary battery including: a cathode including a cathode active material layer; an anode including an anode current collector, and an anode active material layer on the anode current collector, wherein the anode active material layer includes an anode active material which is alloyable with lithium or forms a compound with lithium; and a solid electrolyte layer between the cathode and the anode, wherein a ratio of an initial charge capacity (b) of the anode active material layer to an initial charge capacity (a) of the cathode active material layer satisfies a condition of Equation 1: 0.01<(b/a)<0.5, wherein a is the initial charge capacity of the cathode active material layer determined from a first open circuit voltage to a maximum charging voltage, and b is the initial charge capacity of the anode active material layer determined from a second open circuit voltage to 0.01 volts vs. Li/Li+.