Bi3Ni Solid-State Electrode Structure for Battery Cycle Retention
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Solution Overview
Problem
Lithium secondary batteries face challenges with cycle characteristics due to the expansion and contraction of active materials like silicon and bismuth, leading to poor discharge capacity retention and electron conduction path degradation, especially when using bismuth as an active material.
Innovation Solution
A battery design featuring a first electrode with a current collector and an active material layer containing Bi3Ni, which has a crystal structure of space group Pnma, and a solid electrolyte layer to prevent electrolyte intrusion during charge-discharge cycles, maintaining electron conduction paths and improving cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If bismuth is used as an active material to achieve high capacity, then the discharge capacity is improved, but the cycle characteristics deteriorate due to expansion and contraction during charge-discharge cycles
Solution Approach 1:
The patent uses Bi3Ni intermetallic compound as a composite material that combines bismuth (which provides high lithium alloying capacity) with nickel (which provides structural stability). This composite structure maintains the high capacity benefits of bismuth while the nickel component suppresses excessive expansion and contraction during charge-discharge cycles, thereby improving cycle characteristics.
Solution Approach 2:
The patent changes the crystal structure parameter by specifying Bi3Ni with space group Pnma, which has specific structural characteristics that provide both high lithium alloying capacity and structural stability. By controlling the crystal structure parameters, the material achieves improved cycle characteristics while maintaining high discharge capacity.
2Quantity of substance
If silicon is used as an active material to achieve high capacity, then the discharge capacity is improved, but the electron conduction path degrades due to expansion and contraction
Solution Approach 1:
The Bi3Ni intermetallic compound acts as a composite material where nickel provides continuous electron conduction pathways while bismuth provides high lithium capacity. The intermetallic structure ensures stable electron conduction paths even during volume changes, preventing the degradation issue seen in pure silicon electrodes.
Solution Approach 2:
Instead of trying to prevent expansion and contraction (the conventional approach), the patent inverts the strategy by using an intermetallic compound that inherently maintains structural integrity and electron conduction pathways despite volume changes. The Bi3Ni structure is designed to accommodate expansion and contraction while preserving the electron conduction network.
3Reliability
If a solid electrolyte layer is introduced to prevent electrolyte intrusion, then cycle characteristics are improved, but the device complexity increases
Solution Approach 1:
The patent extracts the harmful component (liquid electrolyte) from the system by introducing a solid electrolyte layer. This removes the source of degradation (electrolyte intrusion into voids) while the solid electrolyte layer itself becomes part of the stable structure, preventing further complexity issues.
Solution Approach 2:
The patent changes the physical state parameter of the electrolyte from liquid to solid, which fundamentally alters the interaction between electrolyte and electrode. The solid electrolyte maintains ionic conductivity while eliminating the intrusion problem, improving cycle characteristics without requiring additional complex protective structures.
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 battery maintains a discharge capacity exceeding 10% of the initial capacity for 20 cycles and improves cycle characteristics by preventing electrolyte intrusion and maintaining electron conduction paths, resulting in enhanced capacity retention and reduced degradation.
Implementation Method 1
a solid electrolyte layer disposed between the first electrode and the second electrode
Implementation Method 2
aluminum, silicon, tin, or the like that electrochemically alloys with lithium during charging
Data Source
AI summary
A battery includes a first electrode, a second electrode, and a solid electrolyte layer disposed between the first electrode and the second electrode, the first electrode includes a current collector and an active material layer disposed between the current collector and the solid electrolyte layer, the active material layer contains Bi3Ni, and the Bi3Ni has a crystal structure of space group Pnma.