Silicon Oxide Negative Electrode with Carbon Coating
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Solution Overview
Problem
Lithium secondary batteries with silicon-based negative electrodes face challenges in high-speed charging due to low electrical conductivity, which limits their energy density and stability during charge/discharge cycles.
Innovation Solution
A negative electrode comprising a silicon oxide-based composite with a crystalline carbon coating layer and artificial graphite with an amorphous carbon coating layer, where the silicon oxide composite is represented by M—SiOx (0<x≤2) and M is an element from Group Ia, IIa, or IIIb, enhancing electrical and lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a silicon-based negative electrode is used to achieve high energy density, then the theoretical capacity increases significantly, but the electrical conductivity decreases making high-speed charging difficult
Solution Approach 1:
The patent uses a composite structure consisting of silicon oxide core particles coated with carbon material. This composite design combines the high capacity advantage of silicon oxide with the high conductivity advantage of carbon, resolving the contradiction between energy density and electrical conductivity. The carbon coating layer provides conductive pathways while the silicon oxide core maintains high lithium storage capacity.
Solution Approach 2:
The patent optimizes the carbon coating thickness and silicon oxide particle size to balance conductivity and capacity. By controlling the carbon layer thickness parameter and silicon oxide particle diameter, the patent achieves both high electrical conductivity for fast charging and high energy density from the silicon-based material.
2Use of energy by moving object
If a silicon-based negative electrode is used to achieve high theoretical capacity, then the energy density improves, but volumetric swelling and shrinking occur during charge/discharge cycles
Solution Approach 1:
The patent employs a composite structure where silicon oxide particles are embedded in a carbon matrix. The carbon material accommodates the volumetric expansion and contraction of silicon oxide during lithium insertion and extraction, maintaining structural integrity and preventing particle disintegration while preserving high theoretical capacity.
Solution Approach 2:
The carbon coating layer acts as a flexible shell that can accommodate the volumetric changes of the silicon oxide core during charge/discharge cycles. This thin film structure provides mechanical flexibility to handle the expansion and contraction without compromising the structural stability or causing particle failure.
3Stability of the object's composition
If silicon oxides are used to reduce volumetric swelling, then stability during charge/discharge improves, but electrical conductivity remains low
Solution Approach 1:
The patent creates a composite material combining silicon oxide with conductive carbon. The silicon oxide provides volumetric stability during charge/discharge, while the carbon component provides the necessary electrical conductivity. This composite approach allows both requirements to be satisfied simultaneously.
Solution Approach 2:
The carbon coating layer serves as an intermediary between the silicon oxide particles and the electrolyte, providing electrical conductivity pathways while allowing the silicon oxide to maintain its volumetric stability. The carbon layer mediates the electrical contact without interfering with the structural benefits of silicon oxide.
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
This configuration enables high-energy density, reduced irreversible capacity, and improved conductivity, minimizing battery degradation even with repeated charge/discharge cycles, while supporting high-speed charging.
Implementation Method 1
a first negative electrode active material having a first core including a silicon oxide-based composite and a crystalline carbon coating layer covering the first core
Implementation Method 2
a second negative electrode active material having a second core including artificial graphite and an amorphous carbon coating layer covering the second core
Implementation Method 3
the silicon oxide-based composite is coated with a carbon coating layer
Implementation Method 4
if the temperature is adjusted within a certain range, silicates can be formed
Data Source
AI summary
A negative electrode which satisfies a need for high energy density while allowing high-speed charging of a battery. A lithium secondary battery including the negative electrode is also provided. The negative electrode includes: a first negative electrode active material having a first core including a silicon oxide-based composite and a carbon coating layer covering the first core including a silicon oxide-based composite; and a second negative electrode active material having a second core including an artificial graphite and a carbon coating layer covering the second core.