Double Layer-Coated Nano-Silicon Electrode for Li-Ion Batteries
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Solution Overview
Problem
Lithium-ion batteries face limitations in specific energy and cycle life due to the volume change, poor conductivity, and unstable Solid Electrolyte Interphase (SEI) formation of silicon negative electrodes during lithium intercalation/deintercalation, which affects their performance and stability.
Innovation Solution
A double layer-coated nano-silicon negative electrode material is developed, comprising a silicon-based nanoparticle with a copper layer and a conductive protective layer, where the copper layer is coated on the silicon nanoparticle, and the conductive protective layer is further coated on the copper layer, using a chemical copper plating method followed by carbon coating and rapid heat treatment to form a copper film, thereby enhancing conductivity and preventing SEI instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode material to achieve high theoretical specific capacity (4200 mAh/g), then the specific energy of lithium-ion batteries is improved, but the volume change during lithium intercalation/deintercalation causes pulverization and poor cycling stability
Solution Approach 1:
The patent applies nested coating structure where copper layer is coated on silicon nanoparticle surface, and carbon layer is further coated on copper layer surface. This multi-layer nested structure effectively manages the volume expansion of silicon during lithium insertion by providing buffer layers, preventing pulverization while maintaining high capacity
Solution Approach 2:
The patent creates a composite material structure combining silicon, copper, and carbon layers. The copper layer provides intermediate expansion buffer and electrical conductivity, while the carbon layer provides structural stability and prevents electrolyte contact. This composite structure resolves the contradiction between high capacity and cycling stability
2Productivity
If silicon particles are exposed to electrolyte to enable lithium ion insertion, then electrochemical activity is achieved, but an unstable SEI film is formed on the silicon surface, reducing cycling performance
Solution Approach 1:
The patent introduces copper layer as an intermediary between silicon and electrolyte, and carbon layer as another intermediary layer. These intermediate layers allow lithium ion transport while preventing direct contact between silicon and electrolyte, thus forming stable SEI on the carbon surface rather than on silicon, which resolves the contradiction between electrochemical activity and cycling performance
3Reliability
If copper is plated on silicon surface to improve conductivity and prevent SEI formation, then electrical conductivity is enhanced, but copper particles form instead of continuous film and cuprous oxide is generated, negatively affecting cycling performance
Solution Approach 1:
The patent performs preliminary carbon coating on silicon nanoparticle surface before copper plating. This preliminary carbon layer serves as a foundation that promotes uniform copper deposition, preventing particle formation and ensuring continuous film formation. This preliminary action resolves the coating quality issue before the main copper plating process
Solution Approach 2:
The patent optimizes plating parameters including copper salt concentration (1-20 g/L), reducing agent concentration (1-20 g/L), pH value (8-12), and plating temperature (20-80°C) to control the copper deposition process. By changing these parameters, uniform continuous copper film is formed instead of particles, and cuprous oxide formation is minimized
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 double layer-coated nano-silicon negative electrode material improves the electrochemical cycling characteristics and conductivity of silicon electrodes, reducing volume expansion and SEI instability, leading to enhanced performance and longer cycle life for lithium-ion batteries.
Implementation Method 1
using a chemical copper plating method followed by carbon coating and rapid heat treatment to form a copper film
Implementation Method 2
followed by carbon coating and rapid heat treatment to form a copper film
Implementation Method 3
using a chemical copper plating method followed by carbon coating and rapid heat treatment to form a copper film
Data Source
AI summary
This invention relates to a double layer composite-coated nano-silicon negative electrode material, and its preparation methods and use, the negative electrode material comprising: a silicon-based nanoparticle, a copper layer coated on the surface of the silicon-based nanoparticle, and a conductive protective layer coated on the surface of the copper layer. Nano-copper has superplastic ductility and conductivity, and the prior art has proved that lithium ions can penetrate nano-copper; therefore, the copper coating layer has effects of inhibiting the volume expansion of the silicon-based nanoparticle and keeping the silicon-based nanoparticle from cracking so that direct contact between the silicon-based nanoparticle and an electrolyte is effectively avoided and a stable SEI is formed, and increasing the conductivity of the electrode. The surface of the nano-copper is coated with a further conductive protective layer to effectively inhibit the oxidation of the nano-copper, thereby improving the electrochemical performance.