Silicon-Graphite Negative Electrode with Swelling Polymer Covering Layer
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries using metallic materials for negative electrodes face issues with gas evolution during high-temperature storage due to expansion and contraction of active materials, which affects their cycling characteristics and storage performance.
Innovation Solution
A negative electrode comprising silicon-containing particles and graphite particles with a covering layer containing a first material that swells with the non-aqueous electrolytic solution and a second water-soluble polymer material, where the mass ratio of the second material to the first is higher than 1, is used to reduce gas evolution during high-temperature storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metallic materials such as silicon, germanium, tin, and zinc are used as negative electrode active materials to increase energy density and power, then the battery capacity is improved, but the negative electrode active materials expand or contract during charging and discharging resulting in poor cycling characteristics
Solution Approach 1:
The patent applies the nesting principle by placing silicon-containing particles inside graphite particles, creating a core-shell structure where the silicon core provides high capacity while the graphite shell provides structural stability and accommodates expansion, thus resolving the contradiction between capacity and cycling characteristics
Solution Approach 2:
The patent uses composite materials by combining silicon-containing particles with graphite particles to form a composite negative electrode active material. This composite structure leverages the high capacity of silicon and the structural stability of graphite, simultaneously improving both battery capacity and cycling characteristics
2Reliability
If an elastic binder coating layer is disposed on the surface of silicon powder to reduce the influence of expansion and contraction, then cycling characteristics are improved, but gas evolution occurs during high-temperature storage
Solution Approach 1:
The patent applies composite materials by creating a multi-component covering layer on graphite particles that includes crosslinking agent-containing particles and polymer material. This composite structure provides both mechanical stability to prevent gas evolution and controlled porosity to accommodate expansion, resolving the contradiction between cycling characteristics and gas evolution
Solution Approach 2:
The patent uses porous materials by incorporating polymer material into the covering layer that creates a porous structure. This porous structure allows the covering layer to expand and contract with the silicon particles during cycling while maintaining integrity at high temperatures, thus improving cycling characteristics without causing gas evolution
3Reliability
If a covering layer containing crosslinking agent-containing particles and polymer material is disposed on graphite particles to suppress gas evolution, then high-temperature storage characteristics are improved, but the structure becomes more complex
Solution Approach 1:
The patent applies merging by combining multiple functions into the covering layer: the crosslinking agent-containing particles provide structural stability, the polymer material provides porosity and flexibility, and together they suppress gas evolution while accommodating expansion. This integration of multiple functions into a single covering layer structure improves high-temperature storage characteristics without excessive 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 reduces gas evolution and improves high-temperature storage characteristics of non-aqueous electrolyte secondary batteries by controlling the expansion of active materials and maintaining electrical integrity.
Implementation Method 1
the first covering material containing particles that can be made to swell with a non-aqueous electrolytic solution
Implementation Method 2
negative electrode active materials composed of metallic materials that can form alloys with lithium and oxides of these metals expand or contract during charging and discharging
Data Source
AI summary
Gas evolution during the high-temperature storage of a non-aqueous electrolyte secondary battery is suppressed to improve the high-temperature storage characteristics of the non-aqueous electrolyte secondary battery. A negative electrode for a non-aqueous electrolyte secondary battery contains silicon-containing particles and graphite particles. A covering layer is disposed on each of the graphite particles. The covering layer contains a first covering material and a second covering material, the first covering material containing particles that can be made to swell with a non-aqueous electrolytic solution, the second covering material containing a water-soluble polymer material. The first covering material is disposed on a surface of each of the graphite particles. The mass ratio of the second covering material to the first covering material is higher than 1.