Polymer-Modified Anode Coating for Silicon Expansion and SEI Stability
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Solution Overview
Problem
Silicon-based and tin-based negative electrode materials for batteries suffer from volume expansion issues during charging and discharging, leading to surface damage, poor cycle performance, and low Coulombic efficiency due to challenges in forming a stable SEI film and high irreversibility of active ions.
Innovation Solution
A polymer-modified coating is applied to the surface of silicon-based and tin-based negative electrode materials, comprising nitrogen and sulfur elements, which enhances the elasticity and toughness of the coating, allowing for better adaptation to volume changes and improved ion retention, thereby stabilizing the SEI film and reducing surface damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based or tin-based negative electrode materials are used to achieve high theoretical gram capacity, then energy density is improved, but volume expansion during charging causes surface cracking and pulverization, leading to poor cycle performance
Solution Approach 1:
A polymer coating layer is applied to the surface of silicon-based or tin-based negative electrode active material particles. This flexible polymer shell accommodates volume expansion during charging cycles, preventing surface cracking and pulverization of the high-capacity core material, thereby maintaining structural integrity and improving cycle performance while preserving high theoretical gram capacity
Solution Approach 2:
The negative electrode active material is constructed as a composite structure with a high-capacity silicon-based or tin-based core and a polymer coating shell. This composite design combines the high energy density advantage of silicon/tin materials with the structural stability and flexibility of polymer materials, resolving the contradiction between high capacity and poor cycle performance
2Use of energy by moving object
If silicon-based or tin-based negative electrode materials are used to achieve high theoretical gram capacity, then energy density is improved, but stable SEI film formation is difficult, leading to fast capacity fading
Solution Approach 1:
The polymer coating serves as a stable outer layer that facilitates consistent SEI film formation. The polymer's flexible nature allows it to maintain structural integrity during volume changes, providing a stable interface for SEI formation and preventing the rapid capacity fading associated with unstable SEI films on bare silicon or tin surfaces
Solution Approach 2:
The polymer coating modifies the surface properties of the silicon-based or tin-based active material, changing parameters such as surface chemistry, wettability, and mechanical compliance. These parameter changes create favorable conditions for stable SEI film formation, addressing the difficulty of SEI stability on high-capacity materials
3Use of energy by moving object
If silicon-based negative electrode material is used to achieve high theoretical gram capacity, then energy density is improved, but electrical conductivity is relatively low, affecting cycle performance
Solution Approach 1:
The polymer coating layer provides a conductive pathway on the surface of the silicon-based active material particles. This flexible shell maintains electrical contact during volume expansion and contraction, improving overall electrical conductivity of the composite material and ensuring stable electron transport throughout charge-discharge cycles, thereby enhancing cycle performance
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 polymer-modified coating significantly improves the cycle performance and Coulombic efficiency of batteries by reducing active ion loss and capacity degradation, while maintaining a stable SEI film and preventing electrolyte exposure.
Implementation Method 1
silicon-based and tin-based materials have serious volume effects, which will cause huge volume expansion during charging
Implementation Method 2
reduce loss of active ions, and reduce capacity loss of the battery
Data Source
AI summary
The present application provides a negative electrode active material, a process, a battery, a battery module, a battery pack and an apparatus related to the same. The negative electrode active material comprises a core material and a polymer modified coating on at least a part of a surface of core material; wherein the core material is one or more of a silicon-based negative electrode material and a tin-based negative electrode material; the negative electrode active material has a weight loss rate satisfying 0.2%≤weight loss rate≤2% in a thermogravimetric analysis test wherein temperature is elevated from 25° C. to 800° C. under a non-oxidizing inert gas atmosphere. The present application can reduce damage to the surface structure of the negative electrode active material, reduce loss of active ions and capacity, meanwhile can well improve coulomb efficiency and cycle performance of the battery.