Silicon Anode Binder Curing for Battery Cycle Life
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Solution Overview
Problem
Lithium secondary batteries using silicon- or tin-based anode active materials face significant volume changes during charging/discharging, leading to reduced battery capacity and shortened cycle life due to inadequate binding forces between the anode active material and current collector, and existing high-temperature processing methods are inefficient and costly.
Innovation Solution
A lithium secondary battery employing a thermosetting material and a curing agent, along with a curing accelerator, as a binder for the anode mix, which is cured at temperatures below 200°C to enhance binding forces and maintain stability during significant volume changes, thereby improving charge/discharge cycle characteristics and reducing manufacturing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature heat treatment (above 300°C) is applied to convert polyamide acid into polyimide for binding silicon-based anode active material, then binding force between current collector and anode active material is improved, but manufacturing time is significantly increased and productivity is lowered
Solution Approach 1:
The invention changes the curing parameters by using a two-stage process: initial curing at 80-120°C for 1-24 hours followed by post-curing at 150-200°C for 1-10 hours. This parameter optimization allows achieving adequate binding force without requiring the high-temperature (above 300°C) and prolonged treatment needed for polyimide conversion, thereby reducing manufacturing time while maintaining binding strength.
Solution Approach 2:
The invention replaces the durable but time-consuming polyimide binder (requiring high-temperature conversion) with a thermosetting resin that cures at lower temperatures. While the alternative binder may have different long-term stability characteristics, it enables significantly shorter curing cycles, improving productivity and reducing manufacturing costs.
2Strength
If polyamide acid binder is used and heat-treated at high temperature (above 300°C) for prolonged time, then binding force is improved, but productivity is remarkably lowered
Solution Approach 1:
The invention optimizes curing parameters by conducting initial curing at 80-120°C for 1-24 hours and post-curing at 150-200°C for 1-10 hours. This two-stage low-temperature process achieves adequate binding force without the prolonged high-temperature treatment required by polyimide conversion, thereby maintaining productivity.
3Ease of manufacture
If conventional binder is used for silicon-based anode active material, then manufacturing process is simple, but binding force is insufficient to withstand volume changes during charge/discharge cycles
Solution Approach 1:
The invention uses a composite binder system comprising a thermosetting resin (such as epoxy resin, phenolic resin, or polyurethane resin) combined with a curing agent. This composite material provides superior adhesion properties that can withstand the significant volume changes (200-300%) of silicon-based anode materials during lithium insertion/extraction, while maintaining a relatively simple manufacturing process through solution casting and low-temperature curing.
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 provides superior charge/discharge cycle characteristics with reduced resistance and prevents separation of the anode active material from the current collector, achieving at least 77% capacity retention after 50 cycles, while significantly shortening the manufacturing process.
Implementation Method 1
a thermosetting material and a curing agent, as a binder, whereby an anode can be prepared within a short period of time via a simplified manufacturing process by applying the anode mix to a current collector and heating to cure the applied anode mix
Implementation Method 2
heating to cure the applied anode mix at a temperature of less than 200° C., and further, superior charge/discharge cycle characteristics of the battery are provided via stable maintenance of binding between active materials and between the active material and current collector
Implementation Method 3
a thermosetting material and a curing agent, as a binder, whereby an anode can be prepared within a short period of time via a simplified manufacturing process by applying the anode mix to a current collector and heating to cure the applied anode mix
Implementation Method 4
silicon (Si) reversibly absorbs (intercalates) and desorbs (deintercalates) lithium ions through the reaction between silicon and lithium
Implementation Method 5
silicon (Si) reversibly absorbs (intercalates) and desorbs (deintercalates) lithium ions through the reaction between silicon and lithium
Implementation Method 6
upon performing charge/discharge processes, silicon, tin or alloys thereof react with lithium, thus undergoing significant changes of volume, i.e., ranging from 200 to 300%
Data Source
AI summary
A lithium secondary battery includes an anode mix including a silicon- or tin-based material as an anode active material, a thermosetting agent, and a curing agent and a curing accelerator as a binder. The anode mix is prepared within a short period of time via a simplified manufacturing process by applying the anode mix to a current collector and heating to cure the applied anode mix at a temperature of less than 200° C.