SiOx Anode Material With Lithium Silicate-CNT Coating for Swelling Control
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Solution Overview
Problem
Current negative electrode active materials, particularly those based on silicon, face limitations in initial efficiency and life characteristics due to low discharge capacity and excessive volume expansion during charge and discharge, and existing carbon coating techniques do not adequately address these issues while also complicating the preparation process.
Innovation Solution
A negative electrode active material is developed comprising a core of SiOx (0<x<2) with a lithium silicate shell and a carbon nanotube coating layer, formed through a process involving mixing SiOx with Li2CO3 and heat treatment in a H2 gas atmosphere, which improves initial efficiency, capacity, and life characteristics while simplifying the preparation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based particles are used as negative electrode active material to achieve high discharge capacity, then capacity is improved, but volume expansion occurs during charge and discharge
Solution Approach 1:
The patent applies nested structure by placing the silicon-based core particle inside a carbon coating layer, which is in turn coated with lithium silicate. This nested arrangement allows the high-capacity silicon core to be protected from volume expansion by the surrounding compliant carbon and stable lithium silicate layers, enabling the core to maintain its discharge capacity while preventing excessive expansion.
Solution Approach 2:
The patent creates a composite material structure consisting of a silicon-based core (SiOx where 0<x<2), a carbon coating layer, and an outer lithium silicate coating. This composite structure combines the high capacity of silicon with the expansion-buffering properties of carbon and the structural stability of lithium silicate, resolving the contradiction between achieving high capacity and preventing volume expansion.
2Stability of the object's composition
If carbon coating layer is formed on silicon-based particle surface to control volume expansion, then volume stability is improved, but conductive path is insufficient and preparation process is complicated
Solution Approach 1:
The patent merges the volume stability function and conductive path function into a single integrated carbon coating layer structure. The carbon layer simultaneously provides mechanical compliance to buffer volume expansion and electrical conductivity to facilitate electron transport, eliminating the need for separate functional layers and simplifying the preparation process.
Solution Approach 2:
The carbon coating layer is designed to perform multiple functions simultaneously: it acts as a mechanical buffer against volume expansion, provides a conductive pathway for electrons, and serves as a template for the subsequent lithium silicate coating. This multi-functionality reduces the overall complexity of the preparation process while achieving volume stability.
3Stability of the object's composition
If conventional carbon coating technique is used to improve volume stability, then volume expansion is controlled, but initial efficiency and life characteristics are not significantly improved
Solution Approach 1:
The patent introduces lithium silicate as an intermediary coating between the carbon layer and the electrolyte environment. This lithium silicate layer acts as a mediator that protects the carbon-coated silicon core from direct contact with the electrolyte, preventing degradation reactions while maintaining volume stability, thereby significantly improving initial efficiency and cycle life characteristics.
Solution Approach 2:
The patent creates a three-layer composite material structure (silicon core + carbon coating + lithium silicate coating) where each layer contributes specific properties: the silicon core provides high capacity, the carbon layer provides volume stability and conductivity, and the lithium silicate layer provides chemical stability and protection. This composite structure collectively improves both volume stability and reliability metrics.
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 use of lithium silicate and carbon nanotubes in the negative electrode active material enhances battery initial efficiency, capacity, and life characteristics by reducing electrode resistance and controlling volume expansion, while the simplified preparation process improves manufacturing efficiency.
Implementation Method 1
The negative electrode includes a negative electrode active material in which lithium ions from the positive electrode are intercalated and deintercalated
Implementation Method 2
performing a heat treatment on the mixed SiOx (0<x<2) and Li2CO3 with a catalyst in a H2 gas atmosphere
Implementation Method 3
performing a heat treatment on the mixed SiOx (0<x<2) and Li2CO3 with a catalyst in a H2 gas atmosphere
Data Source
AI summary
A negative electrode active material which includes a core including SiOx (0<x<2), a shell disposed on the core and includes lithium silicate, and a coating layer disposed on the shell and includes carbon nanotubes. Also, a method of preparing a negative electrode active material as well as a negative electrode and a battery including the same.